Consider this interview, done early March, in which Fauci argues against masks: https://www.youtube.com/watch?v=PRa6t_e7dgI . You don't even have to read between the lines because he explains his reasoning bluntly: "Exactly, that's the point. It could lead to a shortage of masks for people [(healthcare workers)] who really need it." He never at any point thought masks were ineffective. When he did say so in March as you see from this interview, he said it because he was concerned about shortages for medical staff. There doesn't exist evidence with which one can credibly accuse him of committing this sort of revisionism.
Bringing up Kramer betrays a lack of familiarity with Fauci's history. Kramer and Fauci eventually came to be very close friends, and Kramer is on record saying Fauci was LGBT community's best friend. Mullis lost his marbles later in his life, sounding fringe views on HIV, astrology and lots of other stuff. His contribution of PCR technique is undeniably one of the great discoveries in chemistry, but he's not an authority on much else.