I think Trump didn’t understand at the time, he does seem to have a sort of naïveté, The willingness of these people to stab him in the back. I think he bought into the lines that Republicans will rally around other Republicans and not give them bad advice. Not that Fauci is a Republican but as Stanley Milgram experiment in the 60s confirmed, people tend to believe people in white coats.
The advertisers knew this long before the ‘experiment’ did.