The size of the mempool and corresponding elevated fees has to do with the volume of Bitcoin traded. A couple weeks ago Bitcoin shot up from $1500 to $2900 so the volume also increased dramatically. Now we are in a consolidating period which is lower volume, however, as more money comes into cryptos and Bitcoin, the potential for higher fees remains. Bitcoin needs to decide what it wants to be, the "gold" of cryptos or on the cutting edge of technological advances that could make it much faster and competitive with modern cryptos. I understand that they wouldn't want to give up the "gold" status as that is a solid place to be but no one will use Bitcoin for day to day purchases when fees are higher than 5%.