Competition is supposed to help lower prices. If one tennis racket manufacturer overcharges, then another can charge less and steal all their sales.

But if landlord #1 owns an house and overcharges while landlord #2 owns a house and does not, it’s not like landlord #2 gets all the tenants. They still just have one house. There is no way for one of them to win by benefitting tenants. They can however both win by both hurting tenants.

I guess where there is too much housing, one apartment building can keep full occupancy by charging less, while another building across the street might have 60% occupancy because they overcharge. But rarely is there too much supply anymore. And rarely are there such head-to-head commoditized situations.