It always happens when BTC falls, alts fall too and when BTC rises again they fall because Bitcoin Dominance Index goes up which reflects money flow from Alts to Bitcoin. When Bitcoin get stabilized as well as Dominance Index comes down the Alts Markets starts performing. This is the lesson of history in crypto space. I am quite sure when BTC Price will move side ways but stays above 50K then we will again see Rally in Alts.
The general observation for sure with the majority of alts but you've to give some credit to ETH these last few weeks, Bitcoin was going down (before the current 51k rally) but ETH was pushing above 10% gains to almost 4k. Also a nod to defi coins for hitting ATH during all this sideway trading.