For me it's not that Isaac Arthur is monotone, it's the fact that he's so confident about the future that is most relaxing.

Also, it's quite serene listening to him talk about gigantic space habbitats; it's such a good/calming thought that all humanity would be able to enjoy space, have all their basic needs met, saving Earth by offloading our resources exploitation elsewehere; I guess it's an engineer's wet dream :)