This highlights the point that most large predators avoid direct confrontation with worthy rivals whenever possible.
It's certainly possible that the bear could have won a confrontation with the moose. But it might have taken too much damage in the process and degraded its ability to hunt and feed itself. Or even if it got away with it this time, if it engaged in a pattern of getting into fights with moose, eventually it was going to get caught lacking. Get an eye pocked out, a leg broken, a wound to an internal organ, and it's done for good.
Large predators always try to pick fights they know they'll win, and dip from fights where they might take real damage. Herbivores and small predators are more aggressive about fighting above their weight class because their survival depends on being sufficiently scary to dissuade the large predators from attacking them.