That was because Tysons Corner was (and still is) a major hub of the Internet. Initially because of the DOD and military contractors, but a big chunk of Amazon's cloud is located in data centers there and nearby.

This is the area in question:

https://en.wikipedia.org/wiki/Dulles_Technology_Corridor

"It's also interesting to note that the DC area is the #2 (arguably tied with Boston) given how relatively inconsequential that community is now to what we'd consider the tech sector."

Remember, back then it was ARPAnet. ARPA was/is the Defense Departments Advanced Research Projects Agency. If you think the defence department then or now as not part of the tech sector you would be underestimating the investment in technology research made by the DOD.

But of course. California's nascent technology industry was also created by Federal dollars, just look at Ames, Rand, etc, on the left side of the map. The interesting question I was pondering is why the transition from public to private/consumer sector happened in one place but not nearly so much in the other.

I think at a certain point the question becomes very similar as asking why you got a 6 in a dice roll instead of a 3. You can definitely explain it using Newtonian physics but at a high enough level I'm not sure it really matters.

If you look at maps of the modern internnet, DC has an extremely large collection of international cable terminals. a lot of traffic goes throught it.

Several of my professors at the University of Maryland, in the late 70s, had connections to the institutions that had IMPs, like NBS (now NIST), the Pentagon, Mitre, etc. If you asked nicely, they would give you the dialup numbers for the IMP/TIP so you could play on the ARPANET. I had an account at MIT-AI that I accessed that way.