The economics sub-discipline of economic geography was being developed at about the same time as Eternal September.

The key insight (one of the key insights) from that research is that as the absolute cost of transport goes down, previously insignificant differences in cost become important. This leads to to the development of "hubs" - centralization.

(Here we're talking about information transport, and the cost being time per bit.)

But as you say, at the time the tech world could never have believed that centralization was the default expectation, nor designed things to compensate.