Coulson was murdered by Deadpool on Stevil’s street riders, since he’d gotten too close to discovering the whole totally-not-Nazi takeover in the works
Mephisto resurrected him as his agent, his previous admiration for superheroes turned to searing hate, and worked with the Power Elite to turn the screws on the superheroes as part of the superhuman arms race Aaron’s run was alluding to for a time, and to create the current version of the Squadron as programmable automatons
To top off the rumour that Marvel comics was annoyed that AoS maybe did a Hydra takeover arc better with the framework, It’s implied that Coulson’s murdered one of the other AoS characters