See this Reddit discussion:

“The same 5 people moderates 500 of the most popular subreddits”

https://www.reddit.com/r/slatestarcodex/comments/gjl27j/the_...

It appears the original post they are discussing was removed. Seems like Reddit banned the original user who collected this data and deleted their posts.

Another discussion about this:

“Six powermods control 118 of the top 500 subreddits”

https://www.reddit.com/r/WatchRedditDie/comments/gkkfg5/upda...