But that exactly anticipates public ownership of land.
In the second point, remember that our constitution is built on the common law of Britain, which was our legal system at the time of founding the country. "real estate" means, literally, land owned by the crown, and granted as an estate to an individual in fief to the crwon. The notion of crown lands or government land is so pervasive in law that it was not considered worthy of separate mention. Some things are so fundamental they do not merit mention in the constitution - your right to breath the state's air for one.
I'm not sure that holds in the US. When they bought the Louisiana Purchase, for example, and as the borders spread west, it never occurred to them to limit where settlers could settle (aside from Indian treaty lands). They eventually began to police it somewhat, but the idea that government should own the land forever came, when, in Teddy Roosevelt's era?
I believe that is when government ownership of the land solidified and the land was withdrawn from settlement.
I don't oppose federal ownership of real estate for specific purposes but holding large chunks of land in perpetuity is not proper.