One of my kids, STEM field, knows researchers for one of the vaxxes. Said, basically, that the researchers said back then that it wasn't a big adjustment to retool what they already had to rollout a covid vax.
I'll assume (yeah. I know) that the testing for the previous models would be carried over for the covid version. At any rate, kid had no issues with the vax, since they knew and talked to the researchers. It wasn't, to them, anyway, a completely blank paper unknown that was going to be offered.
So If we look at the possibility that Trump, talking directly to front line researchers, heard thesimilar kinds of things, then it was, for him, probably a good and doable gamble to go with a relatively fast rollout than go with the years of lockdown that Fauci was talking about.
What we don't know is if he vaxxes that were eventually rolled out were the same batches that Trump asked about. Was it a bait & switch after Brandon took over, since crooks wouldn't have to worry about oversight, and being blocked by Trump from requiring mandates.
Trump bought up all the vaxxes, too. Maybe he knew there weren't going to be exorbitant research costs involved and used that as leverage to get a good price.
Fauci, on the other hand, may have wanted to blow research smoke up people's asses to drive up the vax price.
Anyway, Trump got his information from levels most people wouldn't be privy to, or understand, on the medical/scientific level, IMO.