Worth remembering that bots often follow celebs to look more human. This doesn't mean that any of the big names necessarily bought followers.
variety.com/2018/digital/n…
The 12% drop (7 million) for Twitter is pretty striking. Too simplistic to relate that directly to the number of bots which were online, but it's a big hit.
Bots are the easiest part of the problem, but still, this was a big decision.