Larger market, larger alumni base, way better recruiting base. Bigger donors. Academics just as good as WSU (both ranked #179 by US News and World Report)
It's primary problem is that it's student body was likely fans of other in-state programs but couldn't get into those schools. But that is all changing. P5 inclusion will accelerate that. They've seen more recent success than BYU even with a new years six win. It's been in transition in shedding its commuter school status.
WSU has just had the benefit of P5 inclusion for the last 50 years.