Seems like they shouldn't be completely shocked since this is his third time leaving the band. I don't know anything about this guy, but from what the article says, it sounds like he has depression.
He really is though. When you talk to bassists that have encountered his playing, he's one of those players that revolutionized their thinking.
I sometimes hang out with a buddy that fronts a sludge metal band, and the bassist is obsessed with Claypool. He rattles off all the bass player reasons, but they all amount to Les treating the bass as a full fledged art, which is why I love his playing.
I still get hooked on My Name is Mud every time I hear it and have to play it a few times before I can move on. Tbh though, as iconic as that song is for the bass line, the drummer (the one the link is about) is just as amazing, and so is the guitar. Both match Claypool's bass creativity very well on that track. Tbh, they always do, but it stands out more on MNIM.
I feel extremely lucky, I got to see them during the Sessanta tour, and again just a few months ago. I know they'll get a great replacement, but the trio of Les, Ler, and Herb is something really special. Herb is one of the greatest to ever do it!