That's just speculation though. It could be happening, sure, but that sounds very risky, and doesn't pass Occam's razor as far as I'm concerned. On Twitter, time and time again, some people will retweet / fav corporate stuff because it's funny or makes them feel good / outraged / etc. Some people love to associate with or promote a brand they like.

Maybe Taco Bell puts a lot of work in creating content that works well on the Reddit frontpage (which would definitely be manipulative, but hey, what are you gonna do), and maybe their own employees at home are upvoting it ("it's for the good of the company"), but I very much doubt the top people at Reddit are making a business out of this, if only because they couldn't justify it to their employees.

It just seems more likely to me that 1) a lot of material is organically upvoted, and it includes corporate stuff from well-known compagnies because a lot of people relate to them 2) some companies are (trying to) game the system in various ways that violate the spirit but not the letter 3) Reddit is trying to extract profit from all that but isn't being very aggressive about it because they don't have very high operating costs, are VC-backed and they'd rather find something that's compatible with the spirit of the platform and sustainable in the long run.