I long wondered why these types of attacks weren't happening on many smaller chains (litecoin/doge others) and I came to the conclusion that the exchanges actually serve as a deterrent as well.
If an attack happened on an exchange-supported coin, the exchanges would change the confirmation rules or pause trades and such until things were resolved. The spectre of exchange intervention is an additional deterrence on these attacks on top of the economic cost of gaining 51%.
Monero is uniquely suited for this attack though because it now lacks the exchange integrations.
Very interesting indeed.