He's a great guy, but sometimes a little hard to follow if you're only taking part in one conversation at a time when he's talking in two and listening to a third because he expects you to be on the ball in your own discussion when he jumps in to drop a tidbit or ask a question like a chess master playing 4 games in the park at once

If it's like simultaneous chess, why isn't the single thread sufficient context for everything that happens in that thread? It just sounds like the guy you're describing has low cognitive empathy and doesn't understand other people's minds. At that point you're just describing a neurodivergent person who may or may not be a genius in certain domains, while being a moron in this one domain that you've described.