if he thought he could succeed in a way to move his career upward , an assistant would consider a lateral move and leave the the program they're in , unless he/she is in line to take the top spot where they're at.
Assistants are terminated all the time and quality replacements are readily available to take that spot.
The problem is with replacing Gleason might not be his termination, but the chances for success as the OC at RU looks to the good ones
But you do make a good point on why someone from the southwest would want to gamble on being successful on the east coast.
But sometimes the chance to advance your career better( even if a lateral move) makes coaches leave their confort zone and take thir skills to a different part of the college landscape.