George Hu cut his teeth under Benioff during the most meteoric rise of both Salesforce and Benioff's celebrity. I would be very surprised if Jeff's desire to be a public facing CEO would even cause George to notice, let alone bristle at.
It's more likely that someone as smart as George might have just looked at the fundamentals of the business and decided it could not keep this up over the long term.
or... it might have just been epic timing too. Probably.
I don't have any direct knowledge, but the gossip flying around internally at the time was that a big part of George leaving Twilio was because he wanted the CEO role, but knew Jeff wasn't going to leave and give it to him.
That was gossip, of course; sure, George may have decided back then that -- even with all the growth he drove -- Twilio wasn't going anywhere long-term.
The fact that George has not taken on a CEO role since tells me that it probably wasn't a driving factor for him. That's conjecture though. I think that role would be available to him at a lot of strong companies if that was his goal.
It's more likely that someone as smart as George might have just looked at the fundamentals of the business and decided it could not keep this up over the long term.
or... it might have just been epic timing too. Probably.