Partial explanation why Trump let Colorado get away.
Donald Trump is proud of reminding the media that he is self-funding his own campaign. There's a trade-off with that strategy: one has to pay one's own bills.
And it seems that Trump has been able to get by in his decades of business "success" with not paying vendors either their full contract price or not at all. There's a better than good chance that position doesn't work when new contractees and/or vendors know about your reputation and want money up front.
It's expensive to run for president, starting with the primaries. Donald Trump could have hired and paid for experts in all the states having primaries. Experts who would have known the idiosyncratic rules and deadlines, etc. to maximize the number of delegates.
While I don't rule out ignorance, it appears to me that Trump has been working his campaign on the cheap, not wanting the spend the money necessary to play by the rules. He's been given millions of dollars of free publicity denied to other candidates of both parties. I honestly think that he expected to win the 1,237 delegates on a shoestring budget, likely stiffing as many consultants and businesses as possible.
But Colorado was a wake-up call that a serious candidate has to spend serious money with no dispensation of the rules set by the national party.