The bear trying to haul itself up the side of the boat was a call to arms for the fishermen. Clearly, the animals wanted their assistance. Although the cub could get a paw on board, it didn't have the strength to haul itself up and out of the lake.
It was stuck there, close to safety but still slowly freezing to death. Simply grabbing the animal's paw and pulling it aboard didn't seem like a good idea - but they did have plenty of fishing equipment around them. Perhaps that would help?