By reducing the price of altcoins, there is an opportunity to attack 51%. As a solution to the problem, I see the creation of a pool of coins and a miner who will switch(temporarily) mining powers to coins in which the possibility of an attack of 51% has occurred(one of the pools received 51% hashrate). Developers and miners will benefit from maintaining and mine on such pools, as this makes the coins entering the pool more crack-free.
There are two possibilities 1 Move to POS
2 Block ASIC by applied asic resistant.
This is an interesting article for you https://www.coindesk.com/ethereum-miner-linzhi-calls-out-project-coders-for-proposed-asic-ban
ETC gets 51% caused by the asic miners are dominating the hash power in the network and that's it. ETC die very soon. RIP ETC.
ASIC is a serious problem in the crypto and ETC is not the first.