Here is part of the ruling - remember one of Kagan's 3 criteria was that the partisan gerrymandering had to be "egregious".
While the case shows evidence of partisan political vote dilution, Van Soelen wrote that the dilution does not rise to the level of gerrymandering that violates the rights of voters. While the maps were intended on “intrenching” Democratic power, Van Soelen wrote that there wasn’t sufficient evidence to prove that they were actually successful in entrenching their power. So, he concludes that the map doesn’t violate residents’ equal protection rights under the state’s constitution.