Pretty cut and dry. Look Chris, to make the kind of recommendations that he made, he should have evidence, and he can't list any that changed his mind (he was quite clear about the futility of general mask use up to that sudden point).
Looking back, we can now see that general masks and Shut Down made no difference in infection rates or death rates. Also, we have seen that the masks and Shut Down had terrible consequences.
But since Fauci cannot be held to being able to see the future, he simply needs to explain what evidence he had to make his recommendation which he gave with complete certitude and the promise of backing by "science".
He lied. He killed people. He stunted children. He ruined lives. He was dead wrong. He shut down the debate by those who wanted to evaluate the efficacy (so much so that he now faces a lawsuit for colluding with social media comapanies to shut down debate on the issue.
He also ruined the reputation of brilliant scientists who found a different finding. He also shut down the investigation into the source of the virus.
I don't know his ultimate motive, but it is easy to guess - fame, the spotlight, adulation, political, or perhaps to avoid detection of his role in contributing funds to the research that created the virus (rather minor in amount in my opinion if so, but also absolutely indefensible whether or not it ultimately lead to the development of COVID-19 since it promoted Gain of Function research - and remember, Trump was making lots of noise about getting to the bottom of "The China Virus").