Easy unswer - Dolan.
So why Jimmy will do this to himself?

If Isiah was a competent GM the Knicks would not suck. He has been here for 4.5 years. Dolan has made bad choices in executives and is stubbornly loyal. He is not to blame because he is willing to put up a boatload of money. He is to blame for letting the incompetence, lack of professionialism, and ego fest that is Isiah's tenure continue. Dolan would probably be a great owner to work for if you were competent at your job.