It was thrown out there for a specific reason, and of course, the DNC jumped into the trap. They said no, their candidate is forbidden to do this debate, and the message got to Bernie supporters that the DNC doesn’t care what they think.
Mission accomplished. Had the DNC jumped all over the opportunity, Trump would have done the debate and charities would have gotten some big donations.
They are being probed and outplayed by D Trump.
To borrow W's phrase, they are misunderestimating.
I believe he looked around and after a while thought, "I can do this, they are a bunch of amateur morons, who are bad for the country"
Not wanting to put words in his mouth and all..