Excerpt:
Most major subreddits show a decrease of between 50 and 90 percent in average daily posts and comments, when compared to a year ago. This suggests the problem is way fewer users, not the same number of users browsing less. The huge and universal dropoff also suggests that people left, either because of the changes or the protests, and they aren’t coming back.
deleted by creator
You have to remember that APIs were used massively by third party apps users.
I don't see a reason to attribute the API related drop more to automation than users stopping browsing reddit because third party app ban.
If you're trying to sneakily manipulate karma and content, you don't want to be doing it through the API, you want it to look like legitimate users so it doesn't get blocked. This usually means some kind of browser automation.
Of course, reddit does so little to combat it, maybe there really were sleazy astro-turfing botnets just accessing the site through the API.
Back in like 2018, reddit posted some user stats, including a list of "most addicted cities". They forgot to scrub the results and Eglin Airforce Base was the top rank.
The fact that it wasn't blocked implies reddit admins are OK with the airforce's botfarm, and would allow them to use the API.
deleted by creator
If I recall correctly (I might be wrong), July/11 was when the 3PAs stopped working. Regardless of that I don't think that those karma farms relied on the API, because as @PoliticalAgitator said they want to avoid shadowbanning.
However, if we follow your reasoning, it's still a fucking dumb move from Reddit Inc. to kill what made the place active. The issue with bots was never their usage, but rather that they went unmarked, pretending to be human beings [re]posting stuff.