Real Delusion wasn't the strongest criminal organization for nothing. They would perform a background check for every member that they would accept into Real Delusion.
Although they weren't assured that Deus wasn't a spy from the Warrior's Association or even another organization, they were assured that Deus wasn't a threat to them mainly because all of the executive members could just launch an all-out attack against Deus if ever Deus went rogue.
When Deus showed off Blue's corpse, White, Black, Red, and Green realized that Deus could have killed them if he had wanted to. Not to mention, they were even confident that Deus could do it with ease.
At that time, they realized that Deus' control over his bone manipulation was frightening. After all, Deus could use his bone manipulation to snap their spine. It wasn't an exaggeration for them to think that Deus had a high advantage over vertebrae creatures.
