reddit has been pushing itself as an "app" more than a website recently, and killed off a lot of third party apps in a move that drove off some longtime users. could just be a sign of a changing userbase, but I won't write off the idea that reddit is becoming more inhabited by bots.
A test would be to compare against technology-oriented subreddits where there isn't money on the table.
All of the measured subreddits in the linked repo also seem like grift-heavy subreddits to me. They're all the stereotypical "get rich selling pickaxes to miners" subs so seeing them infiltrated by "get rich using AI to sell pickaxes" seems almost expected to me.
I'm curious if the trend was similar across all subreddits with a broader set of topics.