IMHo, it's about Trump knowing it was an ambush and being smart enough to not walk into an ambush. When the Muzzie apologist and the Google gaggle all go after Cruz because Trump isn't there a lot of people will be singing a different song.
I suspect that Trump has some loyalists at Fox who warned him about what was happening and going to happen at the debate which is why he pulled out.
Trump is going to get another 5% bump in the polls.
He wins Iowa by 10%+