This is virtue signaling by the Democratic Party for political purposes.
While Franken's a liberal putz, I think he got a raw deal. In the current Pervnado, the careers of men engaged in three general types of behavior are being targeted:
1. Sickos - those who engage in child molestation and other pervy stuff. These includes Louis CK and, arguably, Roy Moore.
2. Abusers - those who exploit a power imbalance to exploit and abuse women. These include John Conyers, Harvey Weinstein and, especially and most unforgivably, Bill Clinton and his cynical, enabling spouse.
3. Adolescents - those who do stupid stuff like pose for a picture with a female admirer and grab her butt. That's basically all that Al Franken did, and as far as I'm concerned, while such behavior is hardly laudable, IMO the proper sanction isn't loss of career, especially if the perp comes clean, apologizes, and promises to behave better in the future.
Franken should haven't have backed down, IMO, but the reality is that the Dems no longer have any use for him, since his replacement, as appointed by a Democratic governor, is more likely to help the Dems retain the seat. Sorry, Al, life used to be all shits and giggles but now you're the martyr for Democratic political correctness.