The problem with forcing DePaul out of the Big East is that Val would look like a complete fool if DePaul finally made a decent hire and they became even somewhat decent. Imagine the egg on the face of the league and the lost money if DePaul became good enough to make the tournament 2 times in 5 years, which is really not completely unfathomable.
When the Big 10 added Rutgers they were nothing better than average in football and terrible at basketball. Since then their football has only become worse and their basketball program, once considered one of the toughest places to win in the entire country has 2 of the top 3 high school recruits committed to them for next season.
Obviously there are deep issues at DePaul but like everybody else they are one decent hire away from adding value to the league.