I don't think we know their true motivation. Anyone can claim to perceive something as racist. We cannot control their sense of offense. The act they claim to be racist may or may not be racist.
But what advocates of critical race theory have found is that, by claiming that something is racist, they can bring pressure on their employers.
That is precisely what happened here. Basecamp is now under tremendous pressure. Plenty of ire has been focused on the co-founders as well as Singer. Singer has quit, though we don't know the facts of the case. Accusations of racism are fatal to one's career, whether or not they have a basis in fact.
Another word for "revealed pattern" is "narrative." Many narratives can be told about the same set of facts. And many of those narratives are deeply subjective, or driven by ideology.
I could take many minor actions by Jane Yang and others at Basecamp and interpret them as a power grab.
To be clear, I know that some people and companies do act in racist ways. Such behavior is illegal and should be punished. But the evidentiary bar to establish that is high. That bar has not yet been met here.
In this case, we have very serious accusations and very little evidence, evidence that can be interpreted in several ways. But Basecamp and Singer have already suffered serious consequences, and the claims have been aired publicly.
So they were able to create a scandal without going through the effort of proving anything.