He got over his brother's death pretty quick eh.
I guess it wasnt about that and he was just done working at that studio. This stuff happens all the time in this industry. A bunch of Sony devs left to work at Initiative and now they are leaving to go back to Sony studios. These guys know what they are worth and switching jobs get them great raises and benefits. There isnt really anything more to it than that.
They could also miss the better enviroment too.