User blog comment:TB Highwind/CSO Korea leaked new content/@comment-29772803-20180828043313/@comment-27843946-20180830031655

There's a theory that CSO2 was a test bed for how CSO would work in the Source Engine. The test was a massive success, so they shut it down and are in the process of porting its content into CSO.

So, no, CSO2 isn't a failed product. It was an experiment.