Do you realize who the delegates are?
There are a few states, like Illinois and Pennsylvania, who have each candidate select their delegates that will represent them at the convention, but the vast majority of the delegates are chosen by the State party as rewards for loyal service. I.e., they ** ARE ** the establishment.
You honestly think that the establishment will rally around Trump? After they are freed, the establishment leadership will come to a backroom deal and spread the word through the delegates who they will all vote for. An establishment candidate will win by 2,000 votes on the second ballot. And Trump and Cruz will have nothing.