It absolutely has a lot to do with how defensive ratings are calculated. It's very teammate dependent and tends to favor big men, particularly big men that rack up steals like he does. As the only big man with a pulse on our team, it shouldn't be a surprise that he was our highest rated defender (also to be clear, he was hands down our best defender in conference play anyways; I'm not trying to argue that he wasn't).
Before all of our other size perished off the planet, our defensive rating was better when Maliq was on the bench than it was with him on the court. It only flipped the other way after he became the only playable guy with any size on the team.