the ethereum miners don't get income. need to come up with something new)
that's a completely different pow algorithm... In this discussion, it doesn't matter what ETH miners think or do, their gear can't influence BTC network's hashrate one way or another...
That being said: I have only looked at the hashrate graph very briefly, but it seems the hashrate has dropped <20% recently. This drop wouldn't be sufficient for a 51% attack, unless the attacker already had loads of asic's that weren't hashing on the bitcoin network to begin with...
I wonder if the mining inefficiency is what caused the price drop of Bitcoin today or whether there is another matter at play here, any thoughts?
Maybe it's the other way around? Because of the price drop, mining became unprofitable for some of the mining farms, so they switched off their gear (or switched to an altcoin that has a better profit ratio)