Short answers, pulled from the story.
Peercoin launched in 2012 as the first functioning proof-of-stake cryptocurrency. This system selected validators based on their holdings of the associated digital currency rather than computational power.
Ethereum made a major transition in September 2022 after several proposals and delays. This switch moved the second-largest cryptocurrency from proof-of-work to proof-of-stake consensus.
Ethereum's switch to proof-of-stake cut its energy use by over 99 percent according to estimates. The technology avoided the computational prowess validation required by traditional mining methods.
Other chains like EOS, Lisk, Tron, and Tezos adopted various delegated or liquid models during this period. Delegated proof of stake employed a two-stage process where stakeholders elected witnesses proportionally to their stakes.
Ether staked at 27% of total supply compared with Cardano at 66% and Solana at 63%. Funds avoiding staking lost about 3% of potential returns annually due to regulatory uncertainty.