I think the priests had some kind of a motive, political or otherwise, against the king, to put him in danger. Their method seems to be to get the king angry.
King Noah is also dependent upon his priests for counsel and suggestions, maybe even approval in some cases. He is the blood-related heir of the kingdom.
Let's examine some of the interactions between the two:
Mosiah 17:11-12 - the king believes the words of Abinadi, and was about to release him, but the priests got him angry again, specifically saying that he (Abinadi) has reviled the king – not the priests or the people.
The fact that Abinadi says that he has suffered himself to fall into their hands is consistent with the fact that the Lord delivered him earlier when the citizens wanted to kill him. See Mosiah 11:26 and Mosiah 17:9.
In Mosiah 12:1, Abinadi does here what I call guerilla prophesying. It's easy to look at it and say, "he came among them in disguise" and think he's crazy when he cites himself in his prophecies, but I think it means something else. I think perhaps these are small groups he is preaching to, individually. Alma (Mosiah 18:1) did the same thing.