No one is questioning his experience, he has years. 25 years to be precise. Why hire this person to be an assistant? He is going to leave for the very first head coaching job that is offered to him.
Why did he leave Illinois? It sounds like he was forced out, because no one leaves a job as a head coach at a national caliber program, to be a volunteer. Clearly he was applying for any job that paid.
Why would a head coach hire some one like this be essentially a stop watch holder? (to use letsrun's favorite job description for a distance assistant).