What happened to Ethereum PoW?

I'm curious to understand what precisely transpired with Ethereum's Proof of Work (PoW) consensus mechanism. Could you elaborate on the key events and changes that led to the transition from PoW to Proof of Stake (PoS)? I've heard there were concerns over scalability, energy consumption, and decentralization, but I'd like a more detailed account of how these issues shaped the shift and the specific implications for the Ethereum ecosystem. Additionally, what does the move to PoS mean for Ethereum's future, and how does it position the network in comparison to other blockchain platforms?