Could it be a generic "vote curve" like Reddit does?
Seems unlikely since it tops out fairly quickly, but it still could be a "topical" soft like cap without specific manual targeting.
Apparently it's deleting the likes, i.e. the people won't see the coloured heart anymore after some time and have to re-like. Might be platfrom issues of course, "eventually consistent" or something like that :)
This has been a Twitter problem since forever. There's some people who's pinned tweet I have liked a dozen times and more, yet when I return to their home the like is gone. I deleted my account a couple of years ago though, to save on time and nerves.
Is Twitter actively deleting likes, or is this some problem with the platform not being able to scale?