@sneakypete They want to bar him because he doesn't stand a chance of defeating the Dim candidate,right?
The mistake we make sometimes is thinking of the Democratic Party and the left as monolithic, with everyone agreeing not only on the goals but on the best political strategy for getting there. And that just isn't the case. They are divided on what to do about Trump. I'd say you could break them down into three basic groups, and I personally know people who would fit in all three. Maybe there's more, but this is how I'd break them up for now.
1)
The completely obsessed Trump haters. These people are pure emotion, and want to do anything and everything possible to hurt him because they hate him with every fiber of their being. So,
anything that is against him -- like trying to keep him off the ballot -- they support, and they support it regardless of whether or not it may help him because they aren't really
thinking at all. Tell them that sketchy prosecutions help Trump, and they just don't care. They just want to vent their own emotional anger in any way they can.
2)
Democrats who think he can win. These people are worried that he can win the general election, so they want to try every legal avenue possible to keep him off the ballot. They also want him to lose the GOP nomination. They view these prosecutions as the best chance of doing that, and hope that they can reach enough independents/RINO's to prevent Trump from winning either the nomination or the general election.
3)
Democrats who think strategically. These people don't believe Trump can win the general election, so they
want him to be the nominee. So they try to sabotage other GOP candidates in the hope that Trump will win, and that they can then clobber him in November 2024. I'd guess that most of them don't expect Biden to be the nominee either.
That's why you can't look for consistency in how "the Democrats" act towards Trump, because they don't all agree on what should be done about him in the first place.