Short answer - getting wet and rusty.

The show was recreating and critiquing an actual event where the driver attempted to cross a frozen stream - didn't work. They anchored a long piece of webbing to the tree and winched the snowmobile out by affixing the other end around the tread. Basically the machine self extricated, without the driver getting wet....

My choice of anchor would involve a rewoven figure 8, along with multiple wraps around the tree. I love redundancy.