I think its because most people are now using SegWit wallet thats why the fees are dropping. With the help of SegWit and the up and coming LN maybe the fees will much more lower than it is today. I did transfer some bitcoin earlier and it was quite fast using SegWit compared to the past few days when im still not using one.
People were already using segwit blockchain. Only few people were using legacy blockchain and they started to leave it as you know. The reason, there is less spam transactions on btc blockchain now.