There is a great misconception that winning "delegates" in a primary means that you get to personally name a person to be your delegate and that you would, of course, pick a loyalist who would never desert you even if there were 100 rounds of voting.
What needs to be understood is that each state is different. And that the process whereby candidates win "delegates" and the process whereby actual human beings are elected/selected/appointed to be delegates to the convention are two different things.
Trump has found this out late in the game and is trying to catch up now.
When he won "delegates" in any given state, what he won in many states was nothing more than a vote from a delegate on the first ballot. After the first (or second, or third, it varies by state) ballot delegates are under no obligation to vote as they are bound based on election results. How could they be? If all delegates were always bound forever, then in this sort of situation you could never get to one candidate with a majority.
None of this is "stealing." It is understanding the rules and making use of relationships formed with people in the various states over time.
So, Trump, like any other candidate will get what he earned in the primaries. Votes on the first ballot. If no candidate has a majority, then the delegates will have to decide in subsequent votes who they can agree upon is acceptable to a majority of them.
All very rational and no "stealing" is involved. The people selected/elected as delegates represent the party and they make the decision when the voters have not given any candidate a majority.
Excellent post