I think you have to separate the admins, who are reddit employees, and the subreddit moderators, who are mostly not.
The admins are ultimately accountable to the CEO, who is accountable to the board and, by extension, the investors. The admins want to maximise traffic, because that maximises their ability to monetise the users. A certain degree of controversial content is actually good for that as long as it remains below the threshold where you start losing advertisers (see 4chan).
Meanwhile, the moderators are usually volunteers, but there are a few very active "powermods" (or groups thereof) who have control over one or more large default subs. This has allowed them to carve out their own personal fiefdoms. Some of them are abusing this power to enforce their own idea of how things should work, or to push their ideology and narratives. Some others (like the infamous GallowBoob) have even found ways to monetise their influence by getting paid to promote content for 3rd parties without disclosing that fact. This often goes hand in hand with abusing their moderator privileges in order to increase visibility of their own posts (e.g. by removing highly upvoted posts from users, so their own posts can take the top spot in that sub).
This is a real problem, but reddit are mostly unwilling to intervene unless there is a large degree of external pressure, like we saw with the "creepshot" subs that got banned in 2013 after the media picked up on their existence and the one user behind a lot of them.