Without a doubt there are cyclical behaviors in bitcoin. For one miners turn their miners on and off as well as use older ones and don't use them when the price is right to do so. constantly fluxing the difficulty and rewards creating reoccurring self fulfilled prophecies. We see the same thing here in the reward pool and use of steemit, with comments and posts. during high Steem and SBD price times their is more activity.

Then you also take into account tax seasons and beginning of the year expenses, as well as end of the year spending of profits. Very common in business, where the big bucks are.