I just think this isn't true. The reality of the situation is almost nobody actually
wants to maintain anything unless they are paid to do so; people just want to throw you patches and have you accept them and then never contribute again. Very, very few developers actually want to maintain anything. The trust barrier is also typically high. I don't just hand out a commit bit for no reason. This is all cultural, sure, but it is what it is. Maintenance isn't fun and people don't like it.
From experience the ratio of random drive-by contributors to people who regularly contribute high-quality code to the point of qualifying as a "maintainer" is something like 20:1 or worse. That doesn't mean they become maintainers, just that 1 out of every 20 might have the chops, if they dedicated to it. This is true even of corporate contributors from well staffed companies; they only want me to accept the patch so they can do something else. I have literally had corporate engineers file reports to me saying "Please do this" (not maliciously, mind you) and when I respond "I don't have time", but actually knew the person in question enough to follow up with "But I would trust you to do this if I added you as a maintainer, since it's not hard", and they still rejected it as, effectively, "too much responsibility." Didn't even get to the point of whether their work would let them have time for it or not. They have no interest beyond that, I can't blame them in a sense.
The idea that most projects actually have enough well-intended, frequent, sufficiently informed contributors to merit any actual "governance" structure at all beyond "Whatever the one or two authors do to make it all work" is completely detached from the reality of my own experience, is all I can say. And that's the reality for most open source projects that aren't stupidly famous, have literally zero monetary funding, and are still very important.