OK, the reaction to this news amongst Illinois fans, at least from what I can tell, is something less than the reaction Purdue fans had to the Matt Painter news yesterday. That's what a few disappointing seasons will do to a fanbase, and understandably so.
But with Athletic Director Ron Guenther likely serving his last few months in office and with a young team perhaps particularly susceptible to transfer risks, this was not an opportune time for a coaching change (not to mention: many Illini fans are still furious that Bill Self spurned them for Kansas, because of what it said about the relative status of their program. What would it say about the status of Illinois if Bruce Weber left for Oklahoma?)
There are lots of costs that come with a coaching change. Recruiting relationships must be reestablished. Buyouts must be proffered, both for the old and the new coach (though if Weber left of his own accord, of course, this wouldn't be a problem for Illinois). There's no guarantee the old players will respond to the new coach, or that they will even stick around to find out.
And then there's the problem that we still have no clue what makes a coaching relationship a success. Michigan can sign the most successful coach in West Virginia history and the architect of spread football, and suffer their worst three year stretch since the Lindbergh Baby Kidnapping. Auburn grabs a 5-19 coach from Ames and wins a national championship and wins a national championship two years later. USC signs an NFL washout and constructs one of the most frightening college football dynasties of all time. These things are more art than science. About the best thing athletic directors can do is make a sufficiently safe selection that they aren't blamed too much if things don't work out. The AD that hires Brad Stevens away from Butler will have instant failure insurance. That's worth almost as much as success itself.
