This is truly a wild analysis. It’s entirely plausible that Black rock owns the longs and Citadel owns the shorts and that they collaborate. But just the circular ownership leading to total dominance of the market by a few hundred people is enough to make this worth reading.
Blackrock and Vanguard are well known of course, and I knew that they own a bit of everything and each other, but this is (with the respect to the general air of tin foil hat) really scary stuff.
The TL;DR of it is basically that everything that is worth owning or financially controlling in the world is owned by a single corporate entity that is impossible to fully grasp. So basically Sauron.