Not really true. Partisan gerrymandering has been determined to be judicable, federally, for basically my whole life. Following the 1962
Baker v. Carr decision that held redistricting to be judicable (and opening the door to the very important
Wesberry v. Sanders and
Reynolds v. Sims cases I mentioned above), SCOTUS made the decision that partisan gerrymandering was judicable and that a partisan gerrymander could be unconstitutional in
Davis v. Bandemer (1986). The court could not agree, however (and struggled over several other cases regarding the issue), on a standard by which a partisan gerrymander could be held unconstitutional. Then as part of the current court majority's onslaught against precedent, they gave up trying, and
Rucho overturned the judicability in federal courts, while still holding that an extreme partisan gerrymander could be a constitutional violation.
And actually, this case at stake in
Moore v. Harper isn't the first time a NC court has overturned a partisan gerrymander. Interestingly, after
Davis v Bandemer, a court in North Carolina cited that case in
Republican Party of North Carolina v. Martin (1992) when they overturned a partisan gerrymander of some judicial districts.
So: partisan gerrymandering has been ruled on many times. The trouble has been setting a workable standard by which it can be deemed unconstitutional- but the idea that partisan gerrymandering is judicable and that a partisan gerrymander
could be considered unconstitutional has been mainstream since at least the 80's. The judicability of redistricting has been a thing since the 60's. This isn't a radical idea, either in the general populace or in the legal world.