This is difficult to write about, think about, and find solid information about. But I will try.
The politics around this are completely warped. Republicans generally hate Fauci because he insisted COVID-19 was a serious emergency that demanded serious measures including lockdowns and masking (and it was).
Democrats love Fauci because:
1) Fauci epitomizes "science" (but "science" is also people with self-interests including their careers and when it comes to assigning blame for a major disaster any group of people can be expected to point their fingers the other way, and science is often wrong).
2) Fauci insisted that COVID-19 was serious (it was of course) and demanded serious measures like masking and lockdowns (it did). Democrats are entirely correct about this but often fail to see the issues in points 1 and 3.
3) The belief that there is no "scientific" reason to believe the Lab Leak Hypothesis (but the Lab Leak Hypothesis has not been disproven either, despite great efforts to do so. Fauci himself initially believed that the Wuhan Meat Market was only an "amplifier" of the pandemic which originated elsewhere, and Fauci this day continues to admit that that it is not impossible that the pandemic originated from a "lab leak"...which meant that someone in a lab first caught the disease from GOF boosted specimens they were working on).
Given that we just had a Senate Hearing in which Fauci refused to answer 100 questions about COVID-19 it might be interesting to see what all of those questions were. But instead, the media and every source I can find is more interested in the politics of Fauci invoking the Fifth Ammendment when he was pardoned by Biden for activities starting in 2014. I have not even found (yet) the questions asked in official Senate documents released to the public.
What we do know is this:
Gain of Function research on several risky viruses was banned in 2014, but the ban was lifted in 2017 because of "stricter oversight."
But starting, in 2014, the NIH funded the EcoHealth alliance to study viruses in Wuhan. This appears to have been to evade the ban. The research in Wuhan continued despite the ban up to the origins of COVID-19 and probably beyond.
Because this research was being done in China, it was not affected by the ban on doing this research in the US, and also the later "stricter oversight" applied to doing it in the US.
It is known that Wuhan Institute of Virology (WIV) was doing research on Coronaviruses that could be characterized as GOF research (though perhaps not by certain definitions of that) in a BSL-2 laboratory (inadequate for the task and outside US oversight) at the time COVID-19 was released. Therefore, a lab leak from WIV remains a highly plausible origin of COVID-19, and several US intelligence agencies (FBI, DOE, and CIA) concluded (with low to medium confidence) that COVID-19 most likely originated from a lab leak as early as 2021 and maintain those conclusions to this day.
We don't actually have enough detail to prove the Lab Leak Hypothesis because China has never allowed anyone else to see critical information about what WIV was doing in 2019, which itself is suspicious, because if this information were not incriminating they would have no reason to hide anything. It is known that several people involved in this research at WIV got sick around the time in question.
Some, typically MAGA, believe that COVID-19 was a Chinese plot, but US involvement in funding similar research in Wuhan somewhat weakens that idea, as well as the fact that China itself was the first to have to deal with COVID-19 and lost lives and considerable resources because of it. There have been others suggesting it was a US plot, and COVID-19 was simply "planted" in Wuhan to disrupt China, but once again the US suffered even more from COVID-19 so if it was a plot it was surely very inept.
There have been panels of scientists (mostly virologists with vested interests at hand) who concluded it was not likely lab leak based on technical details about the virus and the Wuhan Meat Market, but those conclusions are not air tight, so a lab leak remains plausible. It should be noted that no "smoking gun" was ever found at the Meat Market or elsewhere. No evidence of COVID-19 was found in the wild, as has sometimes been done before. All we know is that people in Wuhan were apparently the first to get it (though we can't be entirely sure of that either).
Fauci denies that particular Coronavirus research being done at WIV in 2019 was funded by NIH, and he is correct. However, previous research of that nature WAS funded by NIH through EcoHealth Alliance. What WIV was likely doing in 2019 (and this is what Jeffrey Sachs, who led one task force investigating COVID origins said in 2021) was unfunded research in the anticipation of funding. Like Dr Sachs, I have worked in science and I know this is how labs operate. A cynic could even believe the real research is the "unfunded research," and when the funding finally arrives that research is now virtually complete, and the funding is then mainly used to start research seeking the next funding opportunity, in effect being the "unfunded research" for that. Sachs himself, after leading a panel of scientists investigating COVID origins, came to believe in the Lab Leak hypothesis and has said so in papers and interviews.
Funded or not, the research which may have originated COVID-19 was done in a lab that had previously received funding for doing very similar research, and they could have anticipated funding for that research too eventually.
Because of the risks, and the ban on GOF research in the US, the NIH should not have been funding EcoHealth alliance to do the GOF research anyway in China. Fauci was head of the Infectious Diseases Institute of NIH, and he also reportedly had direct personal involvement in getting EcoHealth funded to do this research in contravention of the US ban. Therefore Fauci himself helped set up the research program which may have ultimately produced and leaked COVID-19. Because Biden pardoned Fauci for all his activities going back to 2014 Fauci cannot be prosecuted for this.
If I may, let me add one more personal observation. People who are paranoid about germs do not go into research in Virology. People who are paranoid about germs avoid going near Virology Departments. Virologists tend to downplay the risks of the research they are sometimes doing, as they would almost have to do in order to do it, and overplay the benefits. It is not clear to this day that GOF research on viruses has done anything useful. Vaccines, for example, are not devised using GOF research. I first heard about GOF research in 2011 (in a Virology Department btw) and I was immediately scared about it. I've also toured a BSL-4 lab (very impressive) and a BSL-2 lab (not where I'd want to work on anything dangerous).
Finally there is one small issue about pandemic handling that also involves Fauci, but has been so warped by the politics we can't get straight answers. Many Republicans and especially MAGA are still convinced today that masks are useless (often along with the unfounded notion that COVID-19 was fake, and the mRNA Covid vaccines caused all the deaths). This is bad, very bad. But even Trump himself got the vaccine which his Operation Warpspeed had helped make possible more quickly than otherwise. Though Democrats often dispute that Operation Warpspeed made the vaccine available more quickly, it specifically helped fund development of the Moderna mRNA vaccine, which proved to be among the most effective or even the most effective, and if the independent Pfizer vaccine work had failed to be useful it might have taken far longer to get a useful vaccine without the Moderna one. As it turned out, both vaccines became available at about the same time, sometimes giving the public a choice, and most likely cranking out shots more quickly than if it had been left to Pfizer alone.
Early in the pandemic, Fauci (and others) emphasized the importance of hand washing (which is relatively unimportant in the transmission of COVID-19 and many other infectious respiratory diseases) and did not tell the public that masking was a good idea. This was not good. (This attitude was and still is common among doctors--including my own PCP at the time--and even in hospitals.) Later, when it was finally advised that masking was important, the public was prevented from getting highly effective N95 masks and instead told to use simple cloth masks, which are not highly effective and generally protect others more than oneself. I see this as a grave error. Instead, all measures possible should have been taken to ensure an adequate supply of N95 masks both for professionals and the general public. There should have been an earlier Operation Warp Speed for making N95 masks as well as vaccines, and/or lifting sanctions to enable buying them from China. I myself would never have appreciated N95 masks unless I had a friend touting them and giving some away. Even today people wear lesser masks without much thought.