He's gotten worse ever since Israel I swear.
I don't think he's been bought blatantly, but I do think he's shown himself to be a career politician. Corbyn shook the tree, got kicked out, then re-contested his seat as in independent against a huge Labour campaign. Sanders doesn't have the guts.
I also wonder if it really is that he's just become a doddering old man, and he's fallen fully for the 'Trumpist' thing. Such an individualist take.