The compromise I've arrived at is that Ursun was worshipped fairly widely by the Ungols, Gospodars, and any other related peoples who encountered bears on a regular basis, but became particularly significant to the Ungols because He's the most prominent God they were allowed to 'keep' after the Gospodars took over and stamped out the worship of the Chaos Gods and the use of Wind magic. It's similar with Tor for the Roppsmenn and Dazh for the Gospodar - very old Gods that were once relatively minor, but rose to prominence after the Khan-Queen united all three peoples under the Widow and the other Gods were discarded.