To say he was a generally great guy really overlooks how awful he was to women. He was no doubt brilliant, but he had some very serious character flaws. And unfortunately, he had an echo chamber of peers and a rockstar celebrity status that only worked to reinforce his shitty behavior and backwards views. It’s not super uncommon for brilliant people to be absolutely nightmares on a personal level. Imagine being an absolutely brilliant scientist that gets married only to be completely forbidden from science and the things you love, and then reduced to being a maid for a madman with tons of insanely particular demands.
He’s not even necessarily doing it because he’s old. He just doesn’t care. His handlers will tell him what to sign anyway. Why would he want to waste time listening to people talk? There’s not as much power in the presidency as he had hoped for. He can’t even get alone in a room with small children anymore now that the secret service is always present. All he’s really got left to live for is waiting for whenever he can give more orders to kill brown people.