I suppose that theory makes a sort of sense, but iirc the Fig campaign for PoE2 was super successful, so I don’t see from their point of view why they would want to miss out. Maybe they asked for too much, like rights to the franchise, and Obsidian couldn’t come to their terms and so looked elsewhere?
EDIT - I was skimming the official forums and read a great point - someone mentioned Paradox did next to no advertising for PoE or especially Tyranny, and maybe Obsidian felt they would get more attention with a smaller publisher. I suppose we’ll never really know for sure.