Why is Ethereum adopting PoS?

There is the following comment on the Reddit forum:

“It’s not possible to start a Proof-Of-Stake cryptocurrency from a distribtion of zero without some kind of distribution mechanism. One way to do this is to utilize a Proof-Of-Work system for distribution purposes in conjunction with the Proof-Of-Stake scheme for security purposes. This is what Peercoin elected to do. Another way is to be exclusively POW for a period time and then make the switch to be exclusively POS. This is what Ethereum plans to do.”

Is this why is Ethereum adopting PoS? An intended plan to use PoW for distribution, then switch to PoS - or is it because they bungled by copying bitcoin’s PoW, and are only now realising that PoW is bad long term news, and so are making the switch.

Ethereum is a dApp platform (decentralized applications), and as such they need more performance. Basically they must make blocks even faster than current 12 seconds.
From what I see this is primary reason.