The "loyalty oath" was never a commitment not to campaign against him in the primaries. That would be a stupid agreement for any of them to make - and if that was the agreement, then Trump broke it long ago with his attacks on Carson, Cruz, Rubio and Bush. How do you have a campaign where you never campaign against your opponents?
The loyalty oath had nothing in it preventing someone from attacking a rival.
It has everything to do with supporting whoever is the eventual nominee.
Your post is off-point.