I'm not sure how many more times you're going to ask me this question, with my answer being some variation of "I have no clue how likely any of the possible scenarios are based on the information I have" without it becoming repetitive. Three more times? Four?
The most COMMON explanations would probably be a trading partner trying to lower Karlsson's trade value by putting Dorion in a spot where he feels he has no choice to but to trade Karlsson and take back less than he wants, or Karlsson's camp trying to pressure a trade for the same reasons (putting Dorion in a corner and reducing the leverage he has). Those would be my top 2 based on literally nothing else other than a gut feeling and common sense. 3rs would be that the rumour is legit, but only a half truth and the real scenario is similar but different, and neither party (team or player) wanted it to get out, but sometimes these things find a way.
The team engaging in character assasination is... Possible. It's not the first thing that I'd consider, though.
All this being said, like I said, there's no way any of us could possibly lean in one direcrion so heavily that we are sure it is the case, unless we are letting our emotions and biases lead us rather than our objective, crirically thinking selves.