The trigger to them cutting ties with Fat Jack was probably them witnessing his treatment of waitstaff, considering how much of a narcissist Jack is he probably treated them like shit and made his former friends realize what a pile of horseshit he is!
I believe that it is actually Jack that cuts his "friends" loose. There is typically a cycle when it comes to being friends with a narcissist: over-valuation, supply, devaluation, and discard. Charles' youtube channel is actually a great study in this process, as is Jumbo and Delicious' owner.
Charles was brought on and praised as being an expert in seafood and fishing on the video Sous Vide in Aged Balsamic Vinegar. The supply came from the videos where they just went out to eat sushi and Arby's fish sandwiches, both of which Charles outright said he wasn't really happy doing. Devaluation came from when Charles started allowing comments on his videos, which lead to Jack throwing him away and refusing to have him on any more videos in two years. When asked in live streams, Jack quickly dismisses the topic as "he's doing his own thing", which is NPD talk for "He's doing something that I disapprove, but can't call out because people will disagree".
Jumbo and Delicious was praised as being the best burger place is Tennessee from Fatty Doo Doo. The supply came from using his bbq sauces on their burgers as well as actual money to go and eat other restaurants' hamburgers and not compare them to Jumbo and Delicious. Jack almost immediately discards them when the owner suddenly passed away, even going so far as to say he'd "think about donating to his funeral".
Hell, even mods of Jack's live stream were used as supply. BestBudz being the best example. Overvalued for their input in chat, supply in deleting comments bitch-boy Jack doesn't like, then devalued and discarded because they said Jack was making people uncomfortable. When Jack removed mod status live during the chat, he got called out for it and there hasn't been a live chat since.