From what we have been told, the decision was made by Hogan two days ago. WWE chose not to inform their fans about it because they were under the impression they could try to talk Hogan out of it.
Hogan's friends apparently encouraged him not to do the show today but he did anyway.
We are not sure how WWE is going to explain his absence just yet, but he is ticked off to the point where he says he's finished with WWE for good.
Credit: WrestlingAttitude.com