A 51% attack means one entity or a team, takes control of 51% of the hash rate that secures the blockchain. This way a reorg is possible and transactions can be invalidated and double spend. It is a scenario that has happened before in blockchains with a low hash rate like Ethereum Classic, Verge, and many more. In fact, except Bitcoin, Litecoin, and a few more, most of the blockchains are not secure at all (not Doge either).
Ethereum has been suffering for over a year from high fees. A solution proposed by Vitalik and other developers is EIP-1559 (EIP: Ethereum Improvement Proposal) which has been approved by developers for July this year with full consensus on the devs part.
However, in Ethereum, just as in Bitcoin, decisions are not just taken by the devs and the rest proceed with implementing them. A truly decentralized network has a community with different constituencies that all have to reach a consensus. There won't be an agreement if the miners are left outside of this. Even with the Ethereum 2.0 upgrade, PoW has not been eliminated yet. Mining with hardware will still be required for many more years, before and if there will be a decision to completely turn to PoS.
Ethereum is in a difficult situation right now. The miners are having profits never seen before and maybe they don't see the dangers of having a congested network for over one year. Developers are moving to other networks that can scale easier as the high fees have left hundreds of projects not used by anybody. Even DeFi and NFT projects have started moving already to other blockchains that offer low fees, no matter if they are more centralized. BSC (Binance Smart Chain) is already attracting many established and startup DeFi projects, while new NFT platforms are ready to take advantage of the weaknesses of a congested network and compete directly with Ethereum.
Ethereum miners are discussing all options as they predict their profitability will shrink with EIP-1559. Even a 51% attack by some miners. There are rumors of miners coordinating and getting ready for this option, which would be a threat to the network stability. While attacking a network when having 51% of the hash rate means trouble and won't help the long-term profitability of miners, it can still be considered a show of force and put these miners in a better bargaining condition.
I am expecting to read a lot more about that in the coming weeks as hash wars in the past resulted in splits, loss of value, and prestige and created too many controversies.
Read and watch more about this possibility:
- https://www.trustnodes.com/2021/03/10/ethereum-miners-plot-51-collusion