The goal of the cartel was to stabilize prices right in the sweet spot to keep the world addicted. Too low and players start losing money, too high and people switch away from oil, too much volatility, and people switch away from oil.

The prices would go down too much, and then infrastructure would rot as production slows down. Then, prices would skyrocket, and so on.

Oil production and distribution is basically infrastructure, like energy or internet. It can't really follow free market dynamics without eating itself.

A healthy cartel means consistent oil prices. Without it, oil may average cheaper over the long term (and almost certainly over the short term), but there will be a lot more variance.