Why? Because he’s short? That’s silly. Some people are fairly shallow I will grant you that. But a short person can be elected president - I have no doubt about that. I am more concerned about the candidates views on policy than their height. Good grief.
He does not appeal to most conservatives and that is the group who vote in primaries, with the exception of a couple of state who have open primaries. That is the reason he won’t be the nominee.