Not sure this part in bold is entirely accurate. In the interviews I've read/heard, Tommy has said he's unwilling to talk about that subject. I think it's fairly clear that there were issues between the two of them. How big a part that played in his departure isn't something I think any of us will really ever know, unless one of them decides to talk about it in years to come.
Had Davidson's appointment not turned out as well as it has, I think this is something that would be drawing a lot more focus from the fans.