“I think what you’re reacting to is that, at the moment, Biden is an unpopular president seeking a second term while Trump is a popular figure inside his party who is winning primary races. I wouldn’t necessarily compare the two.”
Credit to @JoshuaHolland
Actually, post-Bill Clinton’s presidency, it’s not really that much of a surprise.
The party has been pretty much neoliberal ever since, which would explain their hostility toward Bernie Sanders.