If you wanted to buy $10k worth of an ICO, it makes no difference if you buy Ethereum at $50 or at $1k, because these people don't hold these coins for longer than at most 30-60 minutes. That's what drove Ethereum to that high.
Certainly, the large interest in ICO had an impact on the increase in the ETH price. Later, its decline was a consequence of the fact that the developers who collected ETH during the ICO sold and exchanged them for fiat. This is what we can call history and now everything starts from the beginning. The value of Ethereum depends on its adoption and development. At the moment, investors are still afraid that the upcoming fork will be postponed again, which is why I think that by the end of the year the ETH price will not increase and will remain at the same level as it is now.