I wonder if they were any Weld primary Trump general voters? I assume a few socially liberal republicans who didn't like Trump but also didn't like Biden.
NeverTrumpers who were so turned off by the riots and/or the lockdowns that they held their nose and voted for him.
However, given that "people who changed their politics" is a cop-out answer to this question, I'll just say I doubt there were many. Unlike primary challengers to incumbent presidents from years past, Weld actually endorsed the incumbent president's opponent. And I don't see people who voted against Trump in the Republican primary willing to support him in the general unless, like I said, events over the spring and summer gave them that final push.