It was time for Reince to go. Trump tried the carrot approach with the GOP and it failed. Reince was his point man.
For what it’s worth, I don’t necessarily think Priebus betrayed Trump. His conversion to becoming a Trump supporter seemed genuine, and he supported Trump in the general election. I think more likely, he was naïve about his GOPe friends. He thought he could convince them to come on board and support Trump’s agenda. He underestimated their intransigence and evil.
Clearly they’re not interested in working with Trump, so Trump’s moving on to a new, more aggressive strategy and he needs a COS who can help him carry that out.
I think you are exactly right on all counts.