First, I'm not convinced that the original DACA was as bad as emailing Linus a Word kernel patch. But if it were, I can think of another reason that nobody bothered to challenge it: because it's wildly popular and would be politically disastrous to challenge it and tear it down.

As somebody who believes that this court is more motivated by partisan political concerns than legal reasoning, it seems likely to me that Roberts ruled against this not out of true legal principle, but because it would be so wildly unpopular in an election year that he doesn't like the consequences.

There are many realities that seem plausible here.