Surely if you read the article you read the “But You're Still on Facebook and TikTok?” section and don’t need me to explain what it said - but i can summarize:

Twitter is un-aligned with their goals, and has dismal reach. Facebook and instagram are unaligned with their goals and are how they reach a lot of new people.

Not super complicated, tho if i am reading between the lines - calling out the numbers feels like a call to action for other orgs. Suggesting they run their own numbers, and get off twitter.