The first two organizations are almost the same thing as the core team, for all practical purposes (unless you're a lawyer, say). There is very significant overlap in membership. A cosy arrangement, certainly. I imagine that this structure was based on certain practical considerations. Legal advice about IP and whatnot.
I have been working on Postgres (primarily as a Postgres backend hacker) for over a decade now. The people from the first two groups are friends and colleagues. There are problems, but on the whole these people have a significant amount of moral authority for good reasons. They have at least gotten us this far.
The idea that one of the first two organizations from your list are at risk of going rogue is beyond ludicrous. There are certainly legitimate criticisms that one could make about the project's governance, but this isn't one of them.
> It's just that we disagree what the governing bodies of that community should be, believing that the current ones are a great liability and need urgent reform.
This is not reform. This is a clumsily executed power grab.