Your missing some info here. They already knew what happens when a small group of Parahumans takes over, they seen it on alternative earths, they wanted to see what happens to a large amount of Parahumans. It wasn't that Cauldron wanted these parahumans in power, but it was that Cauldron knew parahumans would come to power regardless when society was broken down.
We did see it happen in canon, with the baseline humans paying taxes and lip service to their local Parahuman, the really exceptional normals being vassals, and the Parahumans forming Undersider type groups under their one strongest leader. We see it happen with Taylor, sure there's some resistance but she is the law in her area, she's who the people turn to for protection, and while most of the adults wouldn't be super comfortable with that, the next generation would have been basically raised under her.