I suggest it is hubris, plain and simple. Walters is to blame for letting things come to this, but O'shea's ego will not allow him to accept that his judgement has become and likely always was flawed. As we age, we become more and more set into a our core personalities. Stubbornness/determination is probably a valuable asset as a player but a liability as a coach. The Willy/Nichols incident when O'Shea was fairly new as the Bomber head coach was very telling.