What if Brom was really in Palancar Valley because he was the chairman of the local Society for the Protection of Urgals?
I know this sounds ridiculous at first, but hear me out: Brom wasn't just lying low in Palancar Valley waiting for Saphira's egg to hatch. He was there because he was the chairman of the local Society for the Protection of Urgals.
The more you think about it, the more it actually fits. Brom knows way too much about Urgals for someone who's supposedly spent decades avoiding everyone. Even before Eragon meets one that isn't trying to kill him, Brom keeps pushing back against the idea that they're just mindless beasts. That's a pretty weird stance for a guy whose entire village would happily tell you the only good Urgal is a dead one. Then you've got all his unexplained trips into the Spine. Everyone assumes he's off doing mysterious Rider stuff, but what if he was actually checking in with Urgal communities, documenting human encroachment, and trying to keep the peace? Being the village's weird old storyteller was the perfect cover. Nobody questions where the eccentric old guy disappears to for a few days. Looking back after Inheritance, when the Varden finally recognize the Urgals as allies, it really feels like Brom was just decades ahead of everyone else. The books never come out and say it directly, but honestly I think Paolini left enough clues that it's hard to read it any other way.