These Democrats don’t make any sense.
They should be happy with this ruling because when Trump becomes President he won’t have a free hand to prosecute Biden for acts that Biden performed when he was President.
Perhaps the answer to the cognitive dissonance you've pointed out is that they don't give a crap about Biden as a person. It's all about the Party, and if "Bi-Dun" is really all done, they'll flush him if that's the expedient thing to do.