I think it is the change because of low value of the bitcoin. This is the period where people are not selling any coins at the moment so the proportionality factor of mining and sending of transaction has decreased a lot. I am not sure if you have observed already or not but whenever the prices of the bitcoin increase a lot then there is increase in the fees heavily. This increase in the fee is due to increased transactions, as the increase in price makes people to sell more and more bitcoin to grab the profits and so on. This is what happening today but the only thing is, its happening in the reverse way.