Sanders made very clear from the beginning that he wasn’t going to engage in personal attacks against Clinton. He ran a principled issues campaign, just as was his intent, and all along the way, Clinton attacked, slandered and maligned him while he basically just absorbed that punishment. A lot of us were commenting on this during the campaign. “Why doesn’t he fight back?” There was certainly plenty he could have used; bury her with it. That’s just not the kind of campaign he wanted to run.
He may have even been more effective against Clinton by taking this tack. She was wallowing in mud (and bullshit) from the opening bell and he refused to get down into it with her.