> 7M is the population of a good-size city. Twitter has something like 24M/day active (including bots. lots of bots!).

According to Statista [1], you're off by an order of magnitude (237.8m mDAU), and that number should exclude bots (though I don't know how accurate it is).

[1] https://www.statista.com/statistics/970920/monetizable-daily...