That's just it, Eichorst was hired to fire Bo Pelini. The idiot's who hired him didn't think any further than that. They just assumed he would hire another guy who could win 9 or 10 or maybe more with some luck. But as I've been trying to explain elsewhere, the AD job of hiring coaches isn't as easy as some people think. Eichorst wanted Bielma and almost had him. He got played in the end. So, with no backup choice in mind he found Mike Riley.
A better AD would have established a better relationship with the current coach from the get go and the whole mess maybe never happens. But Bo had been souring people on his attitude, you can't act like Nick Saban and get blown out like Mike Riley it turns out.