> Which is exactly why no one would spend the crazy amounts of money it takes to execute a 51% attack.

There was a recent paper shared here on an article about new type of currency or exchange system. Although I don't understand details, it explained that since 51% of coins are already mined by just a few pools, if these pools orchestrate together, then can break the chain. But unsure how true this is (cannot find the post anymore, sorry)