I do honestly think if Horford knew Walker was here and Hayward would bounce back he would have resigned here, possibly even for a little less money. I have no proof of this, it is just my personal speculation based on a few concepts.
1) Horford is a very cerebral guy and I certainly get the impression that Stevens is more that kind of coach than Brett Brown who seems more of a character development/mentor type of coach.
2) Horford is a very straight shooter and doesn't get involved in any of the off the court marketing stuff (Twitter, instagram, trash talk out of game). I think this is a lot more similar to how they jays operate than Simmons and Embid do who are very into their personal brands. I thought Horford body language during the Embid fight and comments after that fight were very telling.