Well, imagine that the attack is preceded by a long argument between the Ethereum and Bitcoin communities about whether PoW is still a viable technology.

If the Ethereum stakeholders can only prove that they have enough the power and money to mount a 51% attack on Bitcoin, perhaps by showcasing a small and harmless demonstration, then they would have a pretty good argument for why investors should buy into their PoS solution instead.

At that point, all they would need to do, in my view, is to stir up tensions about whether an actual attack will happen just enough for the some of the Bitcoin stakeholders to become uneasy and start migrating to Ethereum instead.

Once this migration has started, Bitcoin's value would drop, which would then make a 51% attack even more affordable. This could thus create a positive feedback loop where more and more investors will start migrating from Bitcoin to Ethereum.

The first ones to move will earn a lot of money, just like the preexisting Ethereum stakeholders, but the last ones to move will have lost a lot.

What do you think, is this scenario pure sci-fi, or does it sound like something that could realistically happen?