[neogodless]

While I'm also not qualified to diagnose the problem, I would imagine it's something like this...

The major internet connections are like superhighways, with major central routers acting like exchanges. If a major superhighway had an accident blocking traffic, there would be personnel stationed at exchanges to help re-route the traffic, though that often occurs too late to prevent a bunch of backups. At any rate, people using Google Maps, Waze, etc. would see the accident and would likely be redirected to alternate routes that would normally be much slower - and would also be slowed down by the influx of higher than normal traffic.

The fact that the internet still worked albeit much slower than usual leads me to believe that something similar happened. While normally my internet traffic might go through a major hub in NYC and then onward to various carriers and hosts, etc. it had to be re-routed around that hub that is normally sub-optimal, and also ill-equipped to handle the spillover. (And in some cases, bandwidth was saturated, and failed altogether for some users for certain usage.)

[overkill28]

The odd thing about this situation though is the geographic location of Brooklyn: on an island. Why would a significant amount of traffic from outside Long Island be going across the harbor to Brooklyn, especially given all the major switching facilities in Manhattan (closer to shore).

[betterunix2]

What makes you think it is only connected to Manhattan? Long Island has submarine cables connected to New England, various points along the East Coast south of NYC, and several transatlantic cables.