Because it was a bubble and it is now going through a correction phase. After a while it will go back up, sell while you're in profit, buy when it is about to rise. Move to alts now - pick a good one!
I already loss 1000$ for bought altcoin.For few month bitcoin is most pump coin in crypto currency and other coin is highly dump.like waves,mgo.So now I deside only stored eth and btc.