December is a holiday month and in January people usually don't have much money left and they don't make big purchases or investment decisions, so February seems like a good time to conduct a sale. Especially if they expect the market gonna go up.
Last bullrun was in December 2017 and I think next will be too. And its not depends of holidays. I think it depends of positive news and we have some big (Bakkt launch on 12th December)
we'll see if BAKKT starts their crowdsale and the price of bitcoin and other altcoins will go up, of course, they will also be impacted well,
hopefully with BAKKT prices can rise like last year