In cases where someone is convicted of sexual assault, of course they’ll be expelled. That’s not the issue. Many victims (some estimates peg the number at 2 out of 3) decline to report assaults because of one obstacle or another. One (among many) is a lack of trust in the university process. The university was under investigation for Title IX violations not too long ago (see: https://www.chicagomaroon.com/2014/02/11/university-under-federal-investigation-for-sexual-assault-policy/), and RSVP (Resources for Sexual Violence Prevention) remains woefully understaffed and underfunded.
This is only the latest stage in a long and troubled history for UChicago (see: https://www.chicagomaroon.com/article/2017/5/1/special-problem-university-chicagos-troubled-histo/), and while the administration certainly doesn’t want students to be assaulted, they’ve put budget and liability concerns first. If you don’t believe you’ll get a fair hearing, why go through the ordeal of the university process? Many victims don’t. This isn’t very effective in catching perpetrators, of course, but it can be a very reasonable choice for any individual.
The easiest solution is to prevent assaults in the first place, and that’s where the university could do more. Right now, sexual violence prevention is entirely in the hands of fraternity members, and compliance with fraternities’ prevention policy is uneven at best (for instance, multiple students reported violations of this policy during the now-infamous FIJI party). As a private university, UChicago has considerable latitude in regulating fraternities, and could force more stringent prevention efforts on fraternities tomorrow if the administration was interested in doing so. Instead, we’re left with self-regulation, and a real sexual assault problem.