It's the financially and politically favorable move. While male students that are expelled could sue for damages (likely tuition, the value of a diploma, and the value of damage to the young man's reputation, maybe $250k), rape victim's suits would result in much larger damages (what do you think the value of being raped is? add that to the value of seeing your attacker around campus, and arguably the emotional damages of lack of justice, likely at least several million, significantly more if a class action suit is filed), the individuals involved could possibly also be sued for criminal negligence, and the university would be subject to loss of ALL federal funding under title IX (as the DOJ and DOE have threatened ~50 schools).

Politically, the university is also under much less scrutiny. Whether for good or ill, nobody takes Men's Rights Activism seriously, while >50% of the population (and certainly more college-age kids) identify as feminists and feminist activism is HUGE and career-threatening on college campuses (read about Laura Kipnis's predicament) for accused rapists and administrators alike. I would argue that men (and definitely affluent white men) are a politically disadvantaged group on today's campuses, and therefore look to the courts for remedy instead of the universities. Men, and more specifically accused rapists, simply cannot exert the kind of political pressure on universities that the feminist movement can and readily does.

Regardless of the truth of the matter (whether we need more stringent policies against rape or more thorough/less biased proceedings), both the legal and political ramifications of mistakes for universities are smaller when the accused are the victims, so universities institute policies that wrongly convict the accused more often than they leave the raped without justice. Honestly, this benefits no one but the university. When the focus (I think) really should be on rehabilitation of the victims and hearing allegations justly and without bias, university resources are becoming consumed with defending processes that nobody thinks is fair, and for good reasons.

** RANT OVER **