One way of thinking about it is how much a sport is skill-based versus fitness-based. Team sports and racquet sports tend to rely more on skill. Cycling and track and field rely more on fitness. A good soccer player isn't going to become a great just by getting a bit fitter, but the advantage given by doping is exactly what it means to be a better cyclist.
This doesn't explain why cycling seems to attract more doping than running. I don't even know if it's true that it does. But there might be something there given the institutional problems cycling has had with doping. Back in the day, it was entire teams doping, with the team staff and doctors in on it, and it's not like they all left when the sport tried to clean up. Either way, the reputation has stuck around.
Running attracts a lot of doping, it's just less publicized. In particular a lot of Kenyan distance runners have been caught recently.
https://x.com/aiu_athletics
Soccer very much depends on fitness too.
Yes, and I remember the years around 1990 when teams with tall men with a lot of stamina and not much else were giving headaches to top teams with top players. But soccer is also a team sport and there are dynamics that go beyond fitness. The morale of a team has a lot of impact. There have been many cases when the same players started playing well suddenly after a change of the manager. Looking at normal workplaces: fire the boss that hates everybody and everybody hate back, put somebody not abusive or toxic in charge, the workers will start performing better.
The parent did not say it doesn't. He said team sports depend more on skill than fitness, which is true.