How did Jehu trick the prophets and worshipers of Baal?

Answer: Called a great sacrifice for Baal

Jehu claimed he would serve Baal more than Ahab and called a great sacrifice, but it was a trick to destroy Baal's servants.

“Then Jehu brought all the people together and said, “Ahab served Baal a little, but Jehu will serve him a lot.”— 2 Kings 10:18 (BSB)