Well the thing is up until now alt coins prices were largely tracking btc. But the extremely quick and large move over the last few days has meant that cor relation seems to have broken as of now.
In general these things always go in cycles when you will have a period where BTC goes crazy and alts go into oblivion the 8k to 20k move at the end of december followed by an altcoin spring from December to January.

Here is the basic principle though :

BTC goes up - ALts go Down
BTC goes Down- Alts go Down
BTC goes Sideways - Alts go Up