He's the third coaching casualty from Mike Munchak's staff, following running backs coach Jim Skipper (who was not renewed) and tight ends coach John Zernhelt.
The Bush move is the most puzzling of the three, only because if any position currently has an up arrow on the Titans, it's linebacker. Akeem Ayers is turning into a building block and Zach Brown got better and better his rookie year. Colin McCarthy has injury concerns, but was elected a captain by the defense in just his second year, and is quite good when healthy.
I don't think Bush is a great coach. While he didn't have talent during his short, failed term as coordinator of the Texans, at least some players there thought he was in over his head. But I wouldn't have put him at the head of the list of at-risk guys.
The issue that will continue to linger for Munchak is Jerry Gray. The coordinator of a defense that gave up the most points in the league and the most points in franchise history remains in place.