I strongly suspect that Franken was sacrificed by his party's leadership because they needed Conyers to resign. Conyers' case involved workplace power-dynamic harassment covered up with taxpayer money. Franken's was just adolescent silly-stuff, like posing for a photo with an admirer and grabbing her ass.
There was no real grounds for Franken to resign; even his sophomoric behavior took place years before his election the Senate, and while the voters didn't know the details of his butt-grabbing they surely knew they were electing a comedian.
But the Congressional Black Caucus demanded that a white transgressor resign if Conyers was to be made to step down. And Franken's colleagues rushed to judgment because of the convenient meme that the Dems were cleaning house of their harassers while the GOP was trying to elect one of theirs.
The pervnado shows little sign of abating, but it would be helpful if some basic ground rules could be set. The crap that should ruin careers is when a superior demands favors of a subordinate, such as, for example, when the President of the United States gets off in the Oval Office by watching an intern writhing on the rug with a cigar. And that behavior, as we all know, was defended by the likes of Gloria Steinem on down.
The least harmful sort of behavior is that indulged in by Franken - a lame attempt at frat-boy humor. Crude, and certainly objectionable, but not the sort that ought to ruin a career. The solution to bad-taste frat-boy humor is for the woman to stand up and tell the offender in no uncertain terms to sod off. That's how it's addressed in the real world, without the intervention of HR departments and the insulting insinuation that women somehow need protection from the ordinary ebb and flow of social interactions.