This has everything to do with Butler, let's follow the course of events and it becomes imminently clear what is going on:
1. Butler was approached by the Tennessee Titans this past offseason to become the DC
2. This move was blocked by the Steelers, as is their right (any move, even from position coach to coordinator can be blocked, as long as it is not to a HC Position)
3. Given that the Steelers had to block the move, it seems fair to infer that Butler was interested in leaving the organization (this is different from when he simply chose not to accept the position with the Colts in 2012 -
http://profootballtalk.nbcsports.com/20 ... -steelers/, notice how no blocking occurred in this instance as the Steelers were able to talk him out of it)
3. According to Gerry Dulac, Butler's contract has expired (
http://www.post-gazette.com/sports/stee ... 1501100138)
4. Given that Butler is now a free agent the Steelers no longer have the ability to block him from taking another job
5. Couple the above with the fact that Butler likely was willing to leave last year (interpretation of the Steelers blocking his interview), one would have to assume that the Steelers were afraid that Butler was absolutely going to leave if he was not the defensive coordinator
6. If Butler is truly the DC of the future (and honestly, Dick L. is NOT), the Steelers absolutely had to make this move and push LeBeau out now
Sorry, Clem, I don't think this has anything to do with LeBeau being unhappy - it was a move by the Steelers to ensure the future of their staff