My theory is that it all goes back to the AJ/Bowles debacle. Those first few years a lot of guys made significant improvements and developed. The teams played hard all game despite being less talented and lacking depth.
This is all speculation on my part, but I think Butch lost his way as a leader after AJ/Bowles. He became unsure of himself. It led to missteps with players that undermined the authority of the staff and himself. It would explain why he favored certain players that didnt seem to deserve it while burying others. All of this was compounded by his own insecurities, need to be praised, and inability to take criticism, especially from the media, which he alienated.
Long story short, I think Butch was a really good recruiter, a solid if limited coach, but just not a strong enough leader/personality for this job. Hes not the first and wont be the last to get eaten up by this job.