The problem is Trump is both the cause and the symptom of a very broken Republican party. He definitely brings out the worst in his supporters, but they also bring out the worst in him. You saw when he tried to encourage vaccines and his supporters turned on him instantly, so he had to quickly back track.

I think, like you said, the only way he can attempt to steer the MAGA-ship at this point is to offer solutions that blatantly look like he's doing it to own the libs. He can't say "get the vaccine because it'll prevent you from dying." He'd have to say, "Biden is trying to take away the beautiful vaccine I created. He wants to give it to illegal immigrants instead of hard working people like you! The deep state is trying to trick you to believe that the vaccine is poison so they can give it to their pedophile leaders so they can be safe, while you good, Christian patriots are dying."

Even then, I doubt it would work.

Unfortunately his strategy was much more cartoonishly evil. By making it so taking the pandemic seriously was a partisan issue, he could make it so people voting in person were disproportionately likely to be his base. Then set up some regulations to prevent states from counting mail in votes until in person voting is done to manufacture a narrative that they're less legitimate and try to stop the count.