https://www.theverge.com/2018/7/11/17561314/twitter-follower-count-decrease-suspended-accounts

Twitter will stop including accounts that have been locked for bad behavior in publicly posted follower counts, the company said today. Accounts that are locked for violating the company’s standards remain frozen unless the owner logs back in and resets their password. From now on, those locked accounts won’t be counted as followers of any account they had followed.

Most people will lose four followers or fewer because of the change, Twitter said. But large accounts could lose hundreds of thousands of accounts. President Donald Trump’s account lost 100,000 followers immediately after Twitter made the change, a Washington Post reporter found, and former President Barack Obama lost 400,000.