What about the will of the people that are voting for Trump?
If Trump gets to 1237, he's the man and the will of those people are duly exercised. If he doesn't, then those delegates are obligated to vote for him on the first ballot. And the RNC set these rules up.
Neither Ford nor Reagan got the necessary requirement and the convention went with Ford. Well, we see how that turned out.
Once the convention heard that speech, they realized they nominated the wrong man. Let's hope we don't have to go down this path. But if it's Trump, a can of orange juice or a waffle, I'm voting for any of those over Hillary. All three are far superior to her. :-)
If they are tied come the convention, then a runoff would be justified, but if one of them is ahead, they win, first ballot.