The latest numbers are such that Twitter's growth is far less than was predicted.Singling out one quarter over a year ago where a loss in users has happened doesn't exactly seem to imply what it is being used to support, in particular since the numbers have been going up prior and since that, with the latest numbers being up 2 million users (which is 14 million more since the mentioned 2015 numbers): https://www.statista.com/statistics/282087/number-of-monthly-active-twitter-users/
I see a trend, how about you?