1. The number of top level competitors that come from a country is highly correlated with how many people play the sport or game, and how much that culture values it. India's cricket team is much more successful than their soccer team. It's not just a numbers game of what the relative population of different countries is.
2. There is a game similar to chess, called Xiangqi, or sometimes just "Chinese chess". This basically supplants chess as a casual game in China. When I lived in China, I saw Xiangqi played in parks hundreds of times but cannot recall a single time I saw standard chess being played.
This is a significant reason that you see fewer casual players on platforms such as this.
3. If you're talking about professional competitions then China has been well represented, with a long standing women's world champion, current women's world champion and recent men's world champion among many others.
Have someone noticed that in comparation with india , china has not so much people in chess competitions ? what happend ?