This isn't absolutely true. If you recall December 2017 the bull run started as early as July that year and ended up going down during January of 2018, even though it started to fall from 19,000$ during December it still managed to go up from 11,000$ to 17,000$ from December 22 to January 6, 2018 making your holiday theory not possible. Holidays for me in the market don't really have an affect or any kind of factor influencing the prices the market itself is the only thing affecting the prices and maybe the news surrounding it. If you don't believe me just check out the charts and you will see no pattern involving Christmas season and Bitcoin's price movement or even the overall crypto market's price movement.