RPI takes into account a team's winning percentage, opponent's winning percentage, and opponent's opponent winning percentage. The winning percentage is setup so that a home win is worth 0.6 wins, road win is worth 1.4 wins, and a neutral site win is worth 1.0. Losses are the exact opposite.
RPI can be manipulated by playing less home games and more neutral site/road games against teams that are likely to have winning records.
RPI is a decent indicator but not the best because of the manipulation that can be done. Pretty much all rankings are worthless until teams have played 15+ and a handful of games in conference play.
Milwaukee's RPI is worse than ISU's because while 3-0, their other 2 wins were at home against teams that have a combined 1 win in which the 2 actually played each other. (Elon & FIU)
I agree the RPI is broken but everyone knows it can be manipulated. It's on Fran for setting up the schedule to take advantage like a lot of other teams do.