I might still not understand but... Landlords have to pay insurance as well. Why would they be the exception. They have all the same costs and also want to make a profit. How can rent be cheaper then?
Two things: first, landlords aren't entitled to a profit, and second, landlord input costs might be completely different from an owner resident.
On the first point, if the landlord's costs are $2000/month, and the market rent for that unit is $1900/month, the landlord would rather lose $100/month on a lease than lose $2000/month on a vacant property.
On the second, it might be that the landlord bought the place when it was much cheaper, or has a much lower interest rate than what is available today. So if the landlord's costs are $2000/month for a property that would now cost $4000/month at today's purchase prices and interest rates, but can rent for $3000/month at a profit to himself.
Similarly, some volume landlords can spread certain costs around and not pay nearly as much as an owner resident. It might cost $1200 to hire a plumber to do a 6-hour job, but it also might cost $150 to simply have a plumber on the payroll to do that job, if you've got enough steady work that it's cheaper to have him around.
Because if you buy a house, it's just you and the bank, so you need to cover the banks risk for you as an individual, meaning higher interest rates. Larger purchases, or a group of houses are covered by different loan types, flexible rates at for example international rated plus half a point.. and that is mich cheaper. The rate might fluctuate.. but if the government strongarms the fed to keep the loans practically free, companies borrow for free plus half a point. And that is a lot of difference.
Also, the landlord is dropping that money into an asset that often appreciates in value. As long as they otherwise have cashflow to cover it, they can afford to "lose" money each month and make a big payday when they sell it.
Because markets aren't perfectly rational. If they were perfectly efficient, no company would ever be able to make a profit at all. But we don't live in that perfect Econ 101 world, and companies can make profits because inefficiencies exist in the economy. As such, sometimes rent can be more expensive than owning.
Because on average, I imagine very few rental homes are brand new constructions/purchases so their mortgage is a couple years old and lower than if someone bought that same home today.