Georgism

How?

Did any landowner create the land that they own? When the land goes up in value making the landowner richer, is it because the landowner has contributed something to the rest of society?

No, quite the contrary, the landowner is reserving a scarce piece of land from the rest of society. They get richer by depriving the rest of us of that value. What gives them the right to exclusively claim it, denying it to the rest of us?

Somebody owning land doesn't deprive others making money because your labor is what determines your success, so they deserve the private property by earning it or by being able to pass it down to somebody else because you can do what you please with your own property.

When the land increases in value and the rent goes up just because the incomes in the area rose, it's certainly not the landowner's labor that determines their success.

And how about if the rent goes down because of the landowner?

Does that ever happen?

If a landowner can lower the rent to increase sales it can.

They never need to. Because of scarcity, the price of land always rises except in extreme, isolated circumstances (e.g. natural disasters).

More people could move into the area to find a home to live in.