The Real Novelty of the ARPANET

"Physical distance was conquered well before the ARPANET by the telegraph. The kind of distance conquered by the ARPANET was instead the logical distance between the operating systems, character codes, programming languages, and organizational policies employed at each host site. Implementing the first packet-switched network was of course a major feat of engineering that should also be mentioned, but the problem of agreeing on standards to connect computers that had never been designed to play nice with each other was the harder of the two big problems involved in building the ARPANET—and its solution was the most miraculous part of the ARPANET story."

twobithistory.org/2021/02/07/a