Give the number of followers for the user who posted the most lists.
number of followers refers to user_subscriber; posted the most lists refers to MAX(COUNT(list_id))
SELECT SUM(T1.list_followers) FROM lists AS T1 INNER JOIN lists_users AS T2 ON T1.list_id = T2.list_id GROUP BY T1.user_id ORDER BY COUNT(T1.list_id) DESC LIMIT 1