Cruz would get many of Trump’s delegates on the 2nd ballot, because he’s done the groundwork to get Cruz supporters in place as delegates. So, even though those delegates (most of them) are bound to Trump on the first ballot, they could change over and vote Cruz on the 2nd ballot. In fact, North Carolina delegates are ALL unbound, so they could all vote however they want on the FIRST ballot, even though Trump won the state.
Granted, there could be delegates in other states who are bound to Cruz on the first ballot but would switch to Trump on the 2nd, but Cruz has done much more work on getting his people elected as delegates.
And why would they do that? Are you forgetting Trump is a billionaire, he can outbid the GOPe. And you are dreaming if you think Cruz will be the nominee out of a brokered convention.