Ultimately I think you are right, but I don't think this is the right way to think about the question. It's not as though they thought they were creating a mono

Ultimately I think you are right, but I don't think this is the right way to think about the question. It's not as though they thought they were creating a monolith on purpose by following a pattern for creating monoliths. They thought they were following best practices and building a distributed system, without single-points of failure. I think a more productive way to think about it might be what's the psychology and practices that led them to be wrong? My best guess is that at some points in the stack DNS is opaque, and at other points, particularly for trained network people, it becomes transparent (i.e. invisible) and disappears (like a mirage), so then they make both the network and physical locks dependent on it (and BGP) and... lock themselves out when it fails.