The tragedy of the commons is the textbook example of why most assets should be owned privately, and is used to refer to failures common in communal ownership.

The example usually given is that of communal land surrounding villages in England many centuries ago. Shepherds also had their own land, but while there was grass on the commons it was in their interest to graxe there instead. The end result was that the land was overgrazed, not looked after and not improved. The fundamental problem is that what is in the best interest of an individual decision maker is not in the best interest of the community as a whole, unless the land is privately owned. Once someone owns the land, they will figure out how to look after it and use it most efficiently, then put that plan into action.

This is part of a broader problem with socialism - that it fails to align the interest of the individual with the interest of the broader community. Capitalism does not make people selfish. Socialism does not make them generous. But capitalism does tend to do a far better job at matching the interest of the individual with the interests of the broader community.

Yeah. But in a democratic socialist society it would be in their interests to do the right thing by the people or they'd be voted out and control of the nation's assets would be handed over to a new government.

The problem is not that the government doesn't want to handle everything well. The problem is that the government is unable to. Voting in someone else who really wants to do the right thing will not make them any more capable.