They lied to advertisers by inflating viewership numbers 35x higher than reality. They sold their top broadcast mechanism to these advertisers, but repeatedly told the viewers that what they were witnessing was community-created content. The "algorithm" had a built-in caste system which was manually manipulated and curated by admins, while they directed mods to convince the community they don't even have the ability to manipulate the rankings. They even allowed the sexual proposition of minors to take place on a daily basis, while both mods and admins were fully aware of it -- never mind the reports, they were sometimes in the chat while it was happening. They permanently banned anyone who discussed any of these issues, without hesitation.
And this list is just the tip of the iceberg of Reddit's Black Mirror-esque methodologies. The moderators are extremely loyal to the admins, because there are significant perks involved, not least of which being that moderators have notably become a hiring pool. It's no coincidence that the mods who are the most willing to lie are the same people finding employment within the company.