It is my understanding that MT was discontinued primarily because a few folks insisted on posting stuff that put Marlin at risk legally. Examples of this were the posting of irresponsible and sometimes downright dangerous reloading data as well as suggestions for the modifications of Marlin guns that weren't factory-authorized. I also heard that Marlin didn't appreciate the constant complaining about manufacturing quality that, in my opinion, overstated the problems considerably.
While I'm sure Marlin didn't like the sometimes nasty and personal discourse, I doubt that had much to do with MT's demise.