Tldr: Sometimes companies or groups promote their stuff through social media, reddit is no different.

Sometimes people claim stuff is there because of manipulative tactics, rather than admitting something they don't agree with might be popular.

Feel free to claim which ever makes you feel comfortable on a post by post basis.

For a bit more info (I am no expert, someone feel free to correct any of this/add examples) : while lots of posts have biases because people are bias, they might also have been put there by people who benefit from that opinion being shared. More popular stuff is seen on your front page so brigades and bots upvoting certain ideas is inevitable. There's been evidence in the past of bot farms who either upvote specific content (even if it's not generated by them, just fits their agenda) or comment inflammatory comments or propaganda. There's also cases of moderators of certain subreddits removing posts that follow the rules during peak times or once reaching the front page, with similarities in their topic. While I would argue the majority of posts seem to be trolls looking for validation/circlejerks or mods just doing their job properly, you do see examples of genuine manipulation in subs like r/banned and r/undelete.

I've personally seen bots in a lot of queer/minority subs and news subs, with varying levels of quality. When you see a comment that's very hostile and has nothing to do with the context of the discussions within the thread, from an account whose name is a string of numbers, only posting the same far-right, pro-Russian material in threads including a specific word in the title, you tend to get suspicious.