China has the most number of Internet connections in the world. Obviously, leaving such a large market was a terrible business idea. Google could have made a lot of money if it had stayed in China. Instead, other companies will make the money that could have gone to them. Google made a big mistake.
Leaving China doesn't make good business sense, but it was the right thing to do for Google. Internet censoring is a huge deal and the tech giant lost billions of dollars in potential ad revenue by leaving China. However, if the Internet search isn't free and uncensored to all, what's the point?