China did dominate. Everybody that invaded China, became Chinese. It's a massive success story. If you're asking why it didn't colonize, that answer can also co

China did dominate. Everybody that invaded China, became Chinese. It's a massive success story. If you're asking why it didn't colonize, that answer can also come down to geography. It's landmass was so good, it literally had no need for colonization. Once Europe chopped down its forests and got everything it could out of mines, it had a surplus of people that craved more things, this drove it to expand outwards. China's just big and resourceful enough to provide. Once it collapsed into one big polity, something made necessary by lack of natural barriers like in Europe preventing individual nations from being able to protect themselves, everybody could work together to build China. Europe's geography just wasn't as good. Good enough to get to colonization, but not good enough to avoid the need to. You see this happening now in the US, which boasts the second best geography in the world after China. We had a few colonies, but really, our landmass provides us with everything we need. It just wasn't good enough without European horses.