… a firing of Fauci would not only be illegal but also make Trump look bad, which he can't afford 100 days from an election.
No such rationale would ever have stopped Obama or Bill Clinton from cleaning house. They and others (e.g., FDR, Truman, Ike, LBJ, Nixon) would have acted decisively, deriding those who questioned their actions or motivations.
Cowardice is an unappealing trait, and trust me, I am not alone in noticing its presence in Trump.