It's not the bots, really, if under "bot" author assume some script or whatever. Bots does not have attention span and could easily keep this "upvote rate" at desired level, just due to their computer nature.

It is human beings who have an attention span, that cause decline of downvotes with time that author observe. So, it is an army of persons who constantly monitor posts and immidiately downvote whatever they don't like. Then, they lost attention to that post and switch to another target, so the upvote rate began to grow.

And every person who do that job have an exact name. And theil employer have an exact name too.

I think it is perfectly possible to create a specific honeytrap for such persons and their employer to uncover their identities and areal. Especially for the author who, as far as I understand, spend a tons of time studying that shithole named reddit.