Possibly. You could even do this if the slashers were active. Just start up your attack instantaneously in between two blocks. Prior to the attack, nobody is cheating. After the attack, nobody is accepting evidence of cheating.

The whole cryptocurrency thing feels like a bit of a metastable equilibrium, but nobody's figured out anything better. Arguably even government-controlled fiat money is not much better - if >50% of the population doesn't like the rules, they will change them - we may be seeing the beginning of this right now, with a lot of people getting dissatisfied with half their income going to the black hole known as "landlords" who own the rights to take your income without producing any value whatsoever.

It might just lead to everyone abandoning your cryptocurrency and using a different one. Since you had to have >50% of the cryptocurrency in order to conduct the attack, you did lose a substantial amount of real-world value (billions or trillions of $) when everyone else stopped using your cryptocurrency.

It's pretty much analogous to if a majority of PoW miners decide to "go their own way" and make a chain where nobody else is invited. What happens then?