China has a long history with basketball. It was one of few western sports that was explicitly kept during the Cultural Revolution. I've read that teamwork and communal nature of the game appealed to Chinese leadership. If you visit China, you'll see recreational basketball courts everywhere. There are courts by the airport, courts outside the Forbidden Palace, etc.
Then with an NBA focused on expanding its international fan base and Yao Ming, popularity grew even more.
Every school in China has a Basketball field. Not common for other team sports.
Edit: Japanese comic “slum dunk” has a huge cultural impact to those were born around 90s. NBA starts broadcasting to China around 95, Jordan, Iverson, Kobe became super idol since then. Not to mention Yao Ming. Also China team sports is pretty weak, only volleyball and basketball stands out(China’s soccer team suck, tell that to any Chinese and they will agree lol)
Cheap to play and doesn't take up as much space as soccer, so good for urban environments. Same reason why basketball is so popular in US inner cities.
Then with an NBA focused on expanding its international fan base and Yao Ming, popularity grew even more.