The post you are replying to explains this in detail.
Google, Facebook, etc all either had products in China or planned products in China but all voluntarily withdrew for various reasons. I imagine low market share vs domestic services was probably the largest reason.
Remember that as soon as you release a service in the West a Chinese clone will spring forth almost instantly. That clone will be much more Chinese then your eventual adaption and as such will you likely struggle to compete with it. Worse yet said clone is probably built by either Alibaba or Tencent both of which have armies of extremely smart engineers, near unlimited cash to sink into new ventures and a near duopoly on the ecosystems necessary to thrive in China.
At the end of the day the Chinese market is just incredibly tough and Western companies (perhaps rightly) don't think it's worth the effort.
No, Google withdrew because it refused to continue censoring results (and this was back before censorship become much more pervasive, in the 2010s). It wasn't a monopoly like in the US but had a good 30% market share (which in China is a lot). FB, which started later, never even got started in China because censorship of individual posts -- even worse than censoring search results -- would have caused an uproar with FB's user base in the US/Europe.
