Landlord is the role of owner, not maintainer/manager of the property. Sure, they can be the same sometimes (even then most of the actual work gets outsourced to professionals), but anyone can enlist the help of a real estate manager. We usually tend to call them janitors.
Also there are huge open funds specialising in real estate (for rent revenue, for dev/resell potential, or both) that have like a 100 property managers that just need to keep their tenants happy. What that actually means is that investors pool their moneys into a fund with fund managers that buys real estate, finds tenants that wound pay a higher rent under certain conditions (eg I want a huge concert hall in the center of our office complex), fund has the capital to make it happen & evicts the current tenants (unless they can match the rent of the place with a concert hall but without actually having it).