The party did not decide who could (or could not) go to the precinct caucii. Any registered Republican could attend. 65,000 people chose to attend their precinct caucus instead of sleeping in or any number of other activities. Those who bothered to attend their precinct caucus then could choose delegates for the county assemblies, and those elected to attend the county assemblies voted who would be elected for the state convention. Likewise for the national.
Trump could have won this if only his campaign had an organization in Colorado that mobilized supporters to attend their precinct caucus. He was well informed on the way that delegates are chosen in Colorado, but it’s as if he really didn’t want to bother and he’s made a conscious decision to not put any effort into states that require delegate selection though the caucus model.
where is your proof that the GOP chose the delegates, I assume that you were not one? This has been the process for Colorado for the past forty years right or wrong. Where was the outrage when this process was originally started? The straw poll that was canceled, was not in any way shape or form connected with the delegate selection process. It was more a weather gauge for the delegates to see who the populace supported, but not vital to the process. When the GOP changed the rules, stating that any such vote had to be binding, the party decided to drop the meaningless vote.