I have a couple of thoughts about the bear traps...
1) A lot of the traps we see are smaller. Obviously not meant for a bear; more like it's meant for smaller game, like a wolf, even though we still call it a "bear" trap. Those smaller traps won't be as powerful, otherwise the traps would amputate rather than trap (and a wolf with an amputated leg can still travel a long ways).
2) Springs wear out over time, especially when they are over-stretched or over-compressed (i.e., a bear trap stretched open for long periods of time awaiting an animal to trigger it). Those traps looked pretty old and rusty to me. They were probably old and worn out, leading to a less powerful trap, but they're still in use because they're still functional and capable of trapping animals. Plus, back then, it probably wasn't feasible for the French fur trappers to travel back home across the Atlantic to buy new bear traps when their current supply starts to wear out; they'd just have to make do with what they had...
