They bend the knee for censorship requirement. (Not only that, they provided machine learning based filtering service for other Chinese search engine at the time)

According to Google, the China government tried to infiltrate Google's internal computer system. In response, Google stopped the censorship over night, and withdraw from China market shortly afterward.

I still remember night, when _all_ Chinese search engine stopped censoring because Google stopped their filtering service.

The China tech company have evolved much since those days, and they are now much better at censoring compare to what Google had in the early days of the internet.