While this is absurdly conspiratorial, there is a grain of truth to it: early on in Reddit's history, the admins created fake accounts and posted on them to boost engagement[0]. More recently, after the blackout and user exodus, /r/de noticed a bunch of new German-language copies of popular English-language subs being created with a bunch of autotranslated comments[1]. So Reddit's administration is not above creating fake accounts and content to juice numbers.
How much of Reddit's engagement is faked is up for debate - I suspect it's less than we think. However, it'd be really funny if, say, when Reddit IPOs, someone at /r/WSB catches onto this and triggers a bunch of people shorting the stock.
[0] https://www.youtube.com/watch?v=zmeDzx4SUME via https://www.themarysue.com/reddit-fake-account-origins/
[1] https://www.reddit.com/r/SubredditDrama/comments/13p889x/red...