In the middle of last year, the Republican National Committee changed the rules for states at the convention. Henceforth, unlike prior years, state delegates would be bound to the popular vote on the first ballot.
Colorado had always let delegates cast their votes as they wanted, but also had Presidential preference straw polls in each of their caucuses. They determined that if they kept those polls, it would bind the delegates. So in August of last year, Colorado announced it would change its caucuses and delete the Presidential poll.
As a result, last August, all the candidates knew they had to make a delegate play in Colorado.
The Trump campaign failed to put down a ground game in Colorado until the last minute and failed spectacularly.
There was no stealing. There were no last minute changes. Trump had since last August and just failed to do anything. That’s his fault, not Cruz’s or the GOP’s.