I think it would be interesting to ask them why they stopped. There is always a lot of whining about the algorithm but I don't think that is the main reason, maybe the fourth or fifth reason. I call it "graduating", people get good at writing and Medium can't provide the next level of writing so they move on to greener pastures, or they get busy in other aspects of their lives and the intense effort to keep writing on Medium just doesn't seem that important. Right before they graduate they often intensely complain about the algorithm but I think that is them rationalizing why they are cutting back or stopping.