This happened from 2014 to mid 2016, a good 18 months. Nothing happened. There have been bigger threats to the network, the revenue of miners isn't currently o

This happened from 2014 to mid 2016, a good 18 months. Nothing happened. There have been bigger threats to the network, the revenue of miners isn't currently one. A threat to the usability of the network would be if 90% of mining power disappeared at the same time, this means it would take 900% longer to confirm a block until the next difficulty adjustment drops the network confirmation time back to 10 minutes. Difficulty adjustments happen every 2016 blocks, each block is supposed to come every 10 minutes. The worst case scenario would be hashrate disappearing right after a difficulty adjustment meaning 2015 blocks will be found very slowly, there could be a max of 4 months of a slower bitcoin network. Makes me wonder what you even mean by death spiral, like what user experience do you expect to happen? Users wouldn't immediately stop using bitcoin because it was slower, they wouldn't even know it would suck, so more likely the unconfirmed transactions would add up, and to ensure getting mined into a block, the users would increase their transaction fees to coax miners to include them first (instead of dropping their transaction completely when they run out of memory). With a higher fee market, this is an even greater incentive for miners to come back on the network, because now the block reward doesn't even matter, since the fees can potentially eclipse it totally. The price of bitcoin would even cease to matter, if there is a dollar figure of fees just there. Miners come back on the network would make the hashrate higher again, before the difficulty adjustment, making blocks confirm faster, instead of slower. This equilibrium is already in the minds of miners, which contributes to them staying on the network so that they don't miss out. This isn't theory, its all happened before.