Yeah, I'm pretty sure most of the money Trump fundraised was from "new converts" of people that never voted until Trump entered politics. And those people are probably tapped out now or disillusioned
The Republican party has long been funded by big donors for so long that the individual member has a deep distrust in individual donations. At the very least, I know my parents are in that boat: they think it's a scam.
It kinda makes them look even more short sighted tbh. Like yeah, you can look at "there's a few polls where he takes from Biden" and call it a day, but it's kinda missing the fact he's lost a lot of relevance already with no signs of stopping.
It's kind of a catch 22: he's stealing votes from the low-info pool, but at the same time if he's not defined at all he'll make no impact by election day. Elevating him can fix that, but that risks those low info voters realizing what they're getting into and then start biting into Trump's numbers as expected.