I don't understand your point. In some alternate reality, there could be some IPv4 internet that was centrally managed and contained like 3 routers and 20 total

I don't understand your point. In some alternate reality, there could be some IPv4 internet that was centrally managed and contained like 3 routers and 20 total nodes? Yeah? What does that have to do with anything? The internet became the internet expressly because it wasn't centrally controlled. If it were centrally controlled from the beginning it would never have outgrown IPv4. See also IPX.