The more I think about it, I bet Jason had everything to do with this decision.
Babe Laufenberg once called Houck "Jason's best friend in coaching." I can see Jerry asking Jason what we can do to improve things, and Jason blames Alexander and stumps for Colombo and Houck to come back. Both are going to be on Jason's "side" going forward, and both (especially Houck) have the added benefit of being very tight with Jerry going way back.
Never underestimate Jason's desire and ability to play politics to preserve himself and his job going forward. If he'll do it with Phillips and Callahan among others, why wouldn't he do it to a newb like Paul Alexander?