ETH at $8k rate is still acceptable in my opinion although it dropped so much than BTC in the past few days. We're probably just expecting that it'll go back to $1k rate after the major dip weeks ago.
I guess it's because of the slowdown of the ICO hype.
Since ETH is the primary platform on which the ICO tokens are issued on, when ICO hype dies off it obviously means that ETH will be less attractive to investors as well. That's just how it works. Also bitcoin dominance has been pretty low, and it's just returning to its normal level. ETH being the second largest crypto has a lot to do with the bitcoin dominance going to all time lows, and now the trend is reversing.
Just normal market volatility. Not everything follows past performance.
Hope this is the real reason. There's a lot of ICO's here and there and it would be good for it to slow down since some of them only becomes scam afterwards.