i think generally we are in a altcoin season and Eth being one of the kings of altcoins does not want to be left behind . But i am actually surprised to see i this high i didn't know it was coming this far when the bull run stated but lets keep watching to see where its running to.
I still don't agree that we are yet in the alt season, because so many altcoins are not growing as expected. We all know why Ethereum is moving uptrend, but for others, something seems to be stagnating, except for few ones among them. Right now BTC is also growing. So, I would say that both BTC and ETH are the main coins allowing the market to grow for now.