Trump never knew what to do because he was aware the manipulable antivax were in his base but also he thought the vaccine might be released early enough to help win him the election, so he didn't want to come out against it either.
The first trump administration still had a mostly intact bureaucratic apparatus with a cadre of career technocrats in positions of authority and influence. The second is oriented very differently.
Also remember that the politicization of masking took a while to spin up, and didn't fuse with and evolve into the current antivax movement until later, when the vaccine was actually in sight. It wasn't a bipartisan wonderland or anything but early covid days was an extremely different political environment from now.
