Often things go like this:

1. Niche refreshing or funny subreddit becomes popular. Power mods request to join the mod team, are rejected by the mods of the sub, who are just normal people like you and me.

2. It hits 100k users, becoming subject to more stringent rules from the admins

3. Incestuous relationship between powermods/astroturfers/reddit admins is used to get the original mod banned (at least accused of "allowing hateful content" or some other false flag)

4. Powermods take over the sub, keep some old mods, but ban anyone speaking up

5. The subreddit is now under the full control of powermods, and becomes an astroturfed echo chamber like the rest of the reddit front page. Sub's front page becomes a mix between the original content and the marketing page for ShareBlue-like organizations.