Stephen Atkinson, the current president of the Warner Bros Entertainment branch, has always been a serious person, always keeping everything professional in every situation. He was known to be a hard ass among his peers, but he always took it as a compliment.
He was a successful entrepreneur who previously worked for Disney media empire as their CFO but switched recently simply because it wasn't presenting any challenges to him anymore. He was with them for over a decade and helped grow the company into a media conglomerate.
With their growth slowing down, he wanted to take on another endeavour, and hence, when he heard the previous president was retiring, he jumped at the chance. It was also a way to clear his existing spot for the younger generation.
It's not like he was that old still; he started managing that position in his mid-thirties, which was like a baby when such positions were considered in the business world.