some people might decide that a very fast dump (say, the Chinese, they can completely trash the dollar singlehandedly just by putting all their paper on the market at once) so as to immobilize the US military machine. Military machines run on oil, and if there's a run on the US dollar, they won't be able to buy it. That would be really bad for my country as they'd probably try to come here and take it by force, but for other actors that might be seen as a small price to pay for stopping the US after the strategic reserve runs out.