It's supply and demand like anything else. The less supply and more demand, the higher the price.
People don't want to purchase homes today, so everybody is renting. Great for us landlords but bad for real estate companies. I can charge much more for my units because I just about have the only game on the block.
But nobody took pity on us during the housing bubble that lasted for years. We couldn't find tenants. Landlords were in hot competition with each other by lowering their prices, just about to the point of taking a loss. Our section of tenants were scant. You had to rent your units out to people you know would probably not make good tenants. But what choice did we have?
So it all works out in the end. And what would you have Republicans do about high rental prices? As RedFish pointed out, it's not a big profit investment and a hell of a lot of work.