It's likely Dr. Fauci intentionally misled the public for "the greater good". He wasn't promoting masks early on, because he saw the full stupidity of the American consumer on display in the toilet paper aisle of every grocery store. By not promoting masks, he was hoping to keep them available for healthcare workers while mask suppliers ramped up capacity. As far as moving the herd immunity number, he doesn't know the number and admitted so in an interview. When he saw it was likely we would reach his first guess, he confirmed upping his estimate to encourage higher vaccination rates.