There’s no formal structure, shares or board meetings

This is an arbitrary list of things and I don’t agree that all corporations have all of these, but I guarantee most cartels have a formal structure, a clear description of ownership, and what qualifies as board of leaders. Most wouldn’t be able to function without it.

sometimes they do just descend into civil war

They compete with rival cartels in all the same ways corporations would if they could (or already do when they can get away with it).

They’re businesses

I’m curious why you’re willing to call them businesses but corporations.