Besides Vitter admitting it, there was hard evidence.
Yes, Franken resigned--under pressure from Republicans, but perhaps more importantly from his own party. Where do we see any self-policing from the GOP? They can't even be bothered to criticize George Santos (unless that changed in the past day or so)--of course, Santos may actually end up being found guilty of crimes. Then will they dump the guy, or will they continue to stand by their (possibly gay, but definitely not Jewish, whose mom did not die in the 9/11 attacks) man?