@cstross The machinery of empire is fine.
(No one is giving up fossil carbon, agriculture remains totally dependent on fossil carbon. The core mechanism of control is as strong as ever it was.)
What we're seeing is a change of ruling class from people with established political and social ties to factions in the imperial heartland to mammonites exalted by wealth and whose social ties are synthetic/cultic. (The analogy with Constantine's conversion is not distant.)