Wolves take kills away from bears regularly, but most normally when they're in packs. That wolf wasn't serious about facing down the bear, looks like berries (or something like that) were all that were at stake.
I've seen similar behavior with foxes and brown bears on Kodiak (no wolves on the island). The foxes will follow bears around in the spring when they're grubbing up roots, to catch the mice and voles that dart away. .