The bottom line is this. Cases are “important” based on whom you ask. And they’re “divisive” when that person’s important cases don’t come out the way they wanted them to.
Those are stupid distillations of whatever data the authors had already laid out. A case is divisive if the electorate considers it so, which means a case is divisive if it's culturally loaded. The only case in the article where the three liberal judges did not align, is one with no obvious cultural loading, about a state requiring companies to agree to be sued there if they do business there. As for whether a case is considered "important", why does it matter whether anybody considers a case important? Why is that even an idea the piece needs to present?