In order to be fully transparent I admit that the active Bitcoin (BTC) addresses have also dropped in this time
frame, but not by such a big percentage.
Old bitcoiners consolidating small amounts into segwit addresses?
Old bitcoiners are
splitting their addresses (and going to segwit) as the old units are beginning to look cumbersome and revealing. You dont want to flash a wad of 500 notes for a coffee in the dodgy side of town.