He would sign it because the argument being put forth is that "he has to have four years to recruit". The argument not being put forth is that he deserves it.
It is entirely opaque to recruits, none of them would ever know what the school's actual commitment to CM is, so it's entirely plausible.
and I do agree that he'd be getting paid something elsewhere if he chose to leave, but it's not going to be $1.3M. So he could very easily decide that his best play is to take 2 non-guaranteed years that allow him to recruit better and gives him a chance to be successful.
I am not an agent or a lawyer and know little about the best practice for contracts of a D1 basketball coach, but I write a lot of contracts and am skilled at negotiating and if I'm offering anyone a contract where they have had dubious historic performance, I am building plenty of outs into the agreement so that if that signatory isn't executing I am not holding the bag if I terminate them. But hey, maybe that doesn't happen if UR doesn't seem to really care about performance on the one metric they stated they cared about 3 years ago, which was making the NCAA tournament.