Ethereum has been making a name for itself for years now and trying to find a way to get it directly instead of buying bitcoin and using bitcoin to buy ethereum. Right now, you can buy ethereum directly without ever having a single satoshi of bitcoin. That allowed ethereum to become big in itself without having a connection to bitcoin. This caused the prices to be a bit separate as well.

With this new upcoming hard fork for example people started to buy ethereum because they believe this hard fork will allow them to carry on better with ethereum, while bitcoin is going up and down a bit and changing places constantly, ethereum was capable of increasing almost double of what it used to be. That is why we can clearly say in normal days ethereum is not really connected to bitcoin anymore. Of course during a bull or bear market where EVERYTHING goes up or down, they still move together as expected.