I think everything was pointing to Joey already having a plan in place to phase CM out altogether.
He started implementing his plan by giving MSM more job duties, including welding, and giving CM other duties with less pay. I think Joey wished CM would quit altogether, and move on.
Even easygoing laid back Joey knew CM had become more of a liability than ever an asset. IMO. He truly had become a thorn in Joey's side.
Imo, Joey knew he would fare far better without CM.
No more complaints about CM. No more shoddy work from CM. No more of CM spending more time at the casinos instead of fulfilling his job duties. No more loans for CM that wouldn't ever be paid back. No more having to support CMs family everytime he went back to jail. No more having to pay for the same material, and supplies twice.
He had every reason in the world to get rid of CM, and no incentive to keep him.
Imo, and this was all in the process of being done before the final strike of betrayal happened, when CM began stealing from Joey's business accounts.
Nothing was ever enough for CM. He wanted more, and more, but was too lazy to work for it.
So CM took what he wanted, just like he had stolen before, and ripped off other victims, pretty much throughout his adult life, filled with criminal behavior.
This time the only way to steal money from Joey, he knew he had to murder them all.
JMHOO