I live in the US where there are plenty of bears, cougars, and wolves.
There's two problems with keeping a bear like this alive:
- Humans are ridiculously easy prey if it is just us vs. an animal with feral instincts and sharp teeth. The only thing we really have going for us physically is that we have terrifying endurance that has allowed us to stalk our prey to death and evolve to the top of the food chain as we are today.
- Once a bear has figured out that humans are easy food, they're going to do what any animal has done and take the lazy way to survive. Even humans do this, if given a choice all of us would rather drive to the grocery store for dinner than to go out and hunt an actual deer for two weeks living on root and berries in the mean time.
Unfortunately how well he knew the risks are irrelevant (and personally I've been to Yellowstone, it's not like there's bears just wandering all over the visitor center). It doesn't matter if he threw a rock at the bear first and she ate him. You cannot have a bear running loose in a park full of children, elderly, and otherwise unarmed people picking them off as food.
Frankly, we should just be thankful they kept the cubs alive instead of euthanizing them as well. They (for the above reasons) could never be raised on a preserve and let back into the wild either, nor can they ever be around humans for any reason other than a zoo.
That's why people around camp grounds here are so super strict about leaving your trash out or littering of any kind. Once you attract a bear to your trash, and they decide it's a good source of food you've basically sentenced it to death.