@edgarblythe,
That's what I thought, too.
They might have threatened to throw their money behind a primary fight in Vermont. Obviously, the ramped up attacks on Jane were a result of Bernie's run...
But, just considering Bernie's situation: he very likely had no idea he'd have the enormous impact he had during the primary, and he probably had to recalculate his path constantly as his support grew. He probably had no idea that he would actually challenge Hillary as a candidate. When that started happening, he probably set some rigid parameters on how not to be legitimately called a spoiler. I guess after mounting a great popular campaign that really showed her flaws, the only way to recover as a team player was to go all out to campaign for the D, no matter what gruesome individual bore the letter or what they did to get it.
Lots of 'probablys'...
It crushed me that he assumed the position dutifully at and after the 'convention,' but, I read that he abruptly stopped speaking to his good friend Nader after he impacted Gore's chances. Did NOT like so-called spoilers.