Cruz is a good guy and I would vote for him if through some miracle he won the primary. But he really has no mass appeal.
I will take semi conservative Trump over semi conservative Cruz because I know he can win.
(Cruz is semi conservative because of TPP, TPA, Corker-Iran, H1B expansion and McConnel support/votes.)
Fair enough, I can think of many reasons to support Trump.
My point is that winning the nomination requires that a candidate eventually get support from other camps. Doing everything humanly possible to insult those other camps is political suicide and Trump is not immune from reality.