He's liked and trusted. The real reason Trump hated Fauci is because his approval ratings were so much higher. But in a larger sense, destroying a figure of endearment and trust is right out of the Russia/Authoritarian playbook, where you want to destroy the ability of citizens to trust any one or anything. It's the flip side of the "fire hose of falsehood" strategy, where you inundate people with alternate explanations for an event (except for the honest one) and try to burn people out so they stop believing it's possible to know the truth. But in the case of destroying a trusted figure, they are trying to destroy trust in anything. They've also done this with government institutions as well.