It’s impossible really to say. This was their official code citation:

Over the past few months, we have carefully recomputed historical votes on posts and comments to remove outdated, unnecessary rules.

I mean on the face of it, maybe they were telling the truth?

But they are a for profit corporation, and that year forward was when the enshittification really began. I guess I just have little reason to believe that they didn’t just alter the algorithm to make it look like there was more engagement than there was.