I should have said miners and developers. Of course you need the hashrate too, but that can be bought. If ETF-BTC can promise higher valuations, miners may follow, since they are economic actors that seek profit.
It is like saying someone will trade the oxygen in their lungs for another chemical element that "might" be more efficient, it either works great or you die.
This might be a bad exaggeration but as someone who has spent almost everything I have on my mining business, I would not take the smallest risk for burning that down, reflect that on others who invested more than I did and probably have debt to pay, nobody in their right mind would risk damaging bitcoin in the way you describing, ya a little more profit for some thing "unethical" is always expected, aside from that, it won't happen.
The main major aspect of Bitcoin POW security is that miners will always try to protect BTC from such attacks that could deem bitcoin worthless, again.