One thing to question is Kane's ego as it has been clear it was not the greatest in the past, which could lead to toxicity surrounding the team as well as in the locker room. The Oilers were in a do-or-die situation in game 6, a win to force a game 7 or a loss to end their playoff ruin early.
Beforehand, afterwards of Kane taunting the LA Kings crowd the Oilers huddled for fist bumps and it seemed like McDavid let him know that the game still had time left, and proceeded to not give him a fist bump.