While the bear definitely could have taken the lion, it does not mean the bear will take the lion.
I don't think the bear was hunting the lion, so the food motivation for fighting the lion doesn't apply. Even if hunting, carnivores often opt to engage in limited risk endeavors. We often call criminals "cowards" because they pick on the old, the you, the sick, or any other unsuspecting persons. They are describing in doing the cowardly thing of laying in wait so as to use concealment, camoflage, etc. to be able to mount an attack that is a surprise to the victim. Limiting risk isn't about being cowardly. It is about being successful. Calling the bad guys cowards is more about us trying to make ourselves feel good about the attacked person, never suggesting the victim was an idiot for being an easy score, poorly watched if the vic is a child, etc. It is all about the bad guy.
In the wild, animals of small size often overcome larger animals that are not goal oriented big animals trying to eat the small animals. If not starving, then the small fighting animal is judged to be too much trouble and the predator moves on.
Sometimes, you simply get a larger animal that has encroached on the territory of the smaller animal, for whatever reason. The smaller animal can drive away the larger animal who sees the smaller animal more as a sort of annoying pest than a threat.
There would probably be a lot fewer of these imbalanced encounters won by the underdogs if animals carried grudges like humans.
The narration sounds like Marty Stouffer from the "Wild America" TV series. As such, the fight is likely staged, not just caught on camera. The cuts to the kitten really drives home the encounter being staged as do the other camera angles. In just what real world natural event would you expect to be able to capture a mountain lion with cubs that fights a bear and be able to do so from multiple camera angles, indicated you had multiple cameras at the unplanned event?
If it is a Marty Stouffer production, then it is almost definite that the event is completely staged and may even be with fully tame animals. He has been quite creative in the making of his documentaries, but the problem is, they aren't really documentaries, but fabrications of what Stouffer thinks you should be seeing in the wild, mixed with some actual wild footage.
http://outside.away.com/outside/magazine/0696/9606diwi.html
As such, the clip cannot be considered of being representative of any sort of real behavior in the wild as it isn't depicting an actual wild event...like Starsky and Hutch isn't real either. That may, in part, account for the lack of gore. Note the lion really made no attempt at the bear's face, nor trying attacking the neck. Instead, the lion batted at the top of the bear's head that was presented to her and bit an ear. These are very non-critical sorts of areas to attack when dealing with an animal many times larger. Notice the bear slings off the cat with a sort of shoulder lob quite easily, then gives up the attack. Note the bear never tried to harm the cat. In other words, the fight was more of playful wrestling than a life and death struggle - staged. The cuts to the overly concerned kitten, bear roar, and cat roar are classic production garbage.
