This is my favorite excuse in sports because they "retiree" almost always comes back out of retirement which leads me to believe they've had enough time with their family.
Moreover, "enough time with" anything you don't normally get enough time with can lead a person to change their mind. We're human -- we can re-arrange our priorities but not our time, so we make decisions and are allowed to change our mind. I have no doubts there's more at play here, but a C-level exec leaving for no particular reason after years of grinding seems perfectly reasonable to me.
He is working for Sky as a commentator at races. Doing the occasional TV commentary is a lot less time consuming, is a lot less stressful, and allows a lot more family time, than driving for the #1 F1 team, against arguably the best F1 driver off all time in Lewis Hamilton
I think there is something to it but I think being a driver, especially as Hamilton's teammate, is all-consuming and super stressful. I think now he can do what he wants when he wants without much pressure. He seems to enjoy the spotlight so that's what he does.
As a parent of two very lively small boys, I can say that "enough time with family" is a thing.