Bitcoin and Ethereum in its current implementation uses Proof of Work, which is a very energy intensive process, and the energy used helps protect the network by ensuring its very costly for bad actors to attack the network.
For newer blockchains like Cosmos, which uses Proof of Stake and Solana which uses Proof of History, they have other mechanisms to protect from a 51% attack, and so does not need the validator/miners to consume energy like the Proof of Work consensus systems.
Proof of Stake protocols typically use variants of BFT consensus, which support only up to 33% malicious voting power. So no, they do not protect against 51% attacks like Nakamoto consensus protocols do.
Bitcoin and Ethereum in its current implementation uses Proof of Work, which is a very energy intensive process, and the energy used helps protect the network by ensuring its very costly for bad actors to attack the network.
For newer blockchains like Cosmos, which uses Proof of Stake and Solana which uses Proof of History, they have other mechanisms to protect from a 51% attack, and so does not need the validator/miners to consume energy like the Proof of Work consensus systems.