Fiduciary duty isn't that big of a deal compared to the general incentive to make money. When CEOs are hired they are screened to be the sort of people who want to make money. If I had a controlling share of a company and the CEO didn't want to make profitable decisions there isn't any special legal construct needed - he'd be gone and somebody new would be hired. Most shareholders are the same.

> ... regardless if they might feel that the community would be better served by using the land for something which would, incidentally, make less money for them personally ...

The community obviously disagrees with our landholder in this scenario, or the community can stump up the cash to pay the land taxes or hold the land publically.

It is just 1 more expense. It isn't like running a soup kitchen was ever free, someone is paying for the soup. Giving a donation of space is the same as giving a donation of time and materials.

There are incentives, but there isn't anything especially new here. It isn't going to be radically different from a mortgage in the short term, and in the long term the change is competent people will own land instead of old families.