Since it's all just speculation, here's my take:
Judging by the wording in all publicly available statements, it very much sounds like something sexual might have been the cause. We also now "know", that it had something to do with a staff member and that he was with he team when the incident occurred.
All this leads me to believe, that he got jiggy with a female staff member (and probably even bragged about it afterwards to someone within the org) despite being married an that the Blackhawks saw this as grounds for terminating the contract, as they want to show how much "they care" and "have changed" as an organization. You know, it sends a powerful message, if your media spin doctors present you as the good guy, and could ultimately be seen as cleaning up after the utter mess the org left behind.
Again, just my two cents and feel free to call me out for it if you want.