This is a very real possibility but how would they benefit from this? With a crashed bitcoin network their existence would be shortlived, thereafter.
They can hold the bitcoin network hostage, that's how they will benefit. They can impose that they be paid for whatever they are doing and we can't do anything about it but heed to their demands. Unless we all move to another coin and forget about the chain they are in. I guess, it has an unpredictable consequence which could lead to great chaos.