This place surely isn't Moomin Valley. It's a lot busier and louder. So Snufkin was just trying to get some peaceful fishing done in one of the fishing spots when the crab creatures started popping up and stealing things.

This falls under things that are not his business. Having not met any crabs in person before he just assumes that's what crabs do. They haven't tried to take his fishing pole yet so it's not affecting him. And he leaves it at that.

He's watching this stranger lecture them and take things back though. Maybe that's their job. To lecture the crabs and heard them around and reclaim the taken items.

"About how often do they go around taking things?" He asks, assuming her knowledgeable about the whole affair. He sure hopes not terribly often...