It’s difficult to guess how much of the dominance is due to the three shows airing as one big block, but I’m guessing that the full night of Chicago action definitely helps.
The mini crossovers between characters feel more organic and connect the three shows into feeling like they really do take place in one world.
The various Chicago shows are up against Empire and The Masked Singer on Fox, Survivor on CBS, and Modern Family on ABC, to name the biggest rivals.