I think he resigned, he thinks it is best if somebody better can run the company better than him. If you read GlassDoor reviews, his employees don't find him favorable, nor the company for that matter. Jagex isn't rated the best company to work which is what I am trying to say. The company needs a better head honcho, which is best if the company is going to thrive again, the same with the game.
The GlassDoor reviews are a great read but the sad thing is it will be yet another 'Friend' that gets the job not the best person for it so back to square one. Nepotism is what Jagex is all about.
Goodbye MMG. You put up with a lot from us players, and some of it wasn't even deserved. Thank you for your role in killing bots. It would have been a shame if the shortsighted bits of code that inevitably kill all games in due course hadn't even been made by the game company.
Thank you for everything you have done for the game, whether it was a good decision or a bad one, I appreciate it very much, best of luck to you Mark! I am sure Pips will do a great job.