Continuity mistake: The position of Rey's right arm changes between the two first shots after we get to see BB-8 thrown to the ground in Canto Bight. (00:55:15)
Continuity mistake: After the scene showing the First Order ships appearing behind the Resistance ships, when Poe Dameron says "It's Snoke's ship. You gotta be kidding me!", the immediate next shot shows him further away and facing a total different direction from Admiral Ackbar. (00:26:30)
Continuity mistake: When the light saber breaks in half, Ben is thrown to the left of the throne while Rey is thrown to the right. Once Ben wakes up, he is on the right of the throne, exactly where Rey was when she refused him. (01:51:50 - 01:55:10)
Continuity mistake: When Rey meets Luke for the first time, the sun changes between shots.
Continuity mistake: While Rey is practising with the pole and the lightsaber, the sun changes between shots.
Answer: Kylo Ren has betrayed the First Order. They were loyal to the First Order. You are assuming they only did so out of fear of Snoke rather than out of loyalty.