They most likely did something illegal or at least something that puts them on very shaky ground if they try to litigate. I am guessing there are multiple other people they fucked over and those people are not as ethical as this person. So they chose the blackhat path. I would treat any Windows device as a comprised device. It is possible that there are 20 other people, who are the best of the best security researchers, that were taking the low effort paycheck because it was a legal route that are now going to fuck Microsoft up. The non technical people who made the decision to stop paying out, did not fundamentally understand what they were doing. Mythos was just marketed as the best model for doing security research and they fell for it.