there's pretty much never going to be proof of sexual assault. when multiple credible accusations go ignored because "the man didn't admit it," you're giving people the go ahead to sexually assault others with impunity. as long as they deny it, many will believe them. why ever stop?
"Pretty much" never going to be proof? Uh, lol, no.
"Credible" accusations? Lol, no.
Press charges. Formally document your accusations. Move the process into the judicial system. There are both civil and criminal remedies.
Don't rely on the kangaroo court.