I'm not the best at doing this, myself, but I think lin_fusan described the key MC maneuver: as soon as we meet one NPC who has a strong connection to a PC - whether through asking questions, an actual scene, or some connection to their moves or resources (Hardholders with gangs, etc.) - the MC should immediately pivot to another PC and ask a question that establishes a second connection of some kind.
That pivot -- literally turning from one PC's player to the other -- ensures that there are very few NPCs who end up in isolation, relating to only a single PC in a straightforward way.
I don't think the question needs to be that complicated, either, or the 'secondary' connection that immediately-meaningful. As long as there is enough there to develop later, you are guaranteed a triangle. And not every triangle has to immediately erupt into conflict -- if you have enough of them, that sort of thing will emerge naturally out of your other MC moves, Fronts, etc.