I guess it's too much to expect any company, even the "do no evil" one, to stand up for principle when there's so much money at stake.
Especially when it's doing absolutely no good. It made sense for Google to stand up to China when it appeared that there was a good chance they could win. But China won. The absence of Google's services did not cause the Chinese people to demand it, and the Great Firewall was successful at blocking and degrading Google's services enough that people largely don't bother. VPN services exist, but the Firewall makes them unreliable and short-lived solutions, so the Chinese just don't use Google much. And those who are doing all of the work to get around the Firewall are those who will do that work to get to uncensored search services anyway.
So, money aside (not that Google is ignoring the money), there's really nothing to be achieved by staying out of China, and at least some possibility of achieving something by being in China.