Batter passes runner

[Tony B]

I need a little help with a ruling.

Bases are loaded. There is ONE out. The batter hits a long fly ball that barely clears the fence for a HR. All runners had been tagging. The batter/runner passes the runner on first. I realize the batter/runner is out (for out #2). But, what is the ruling on the other runners? What, if any, is their advancement? I would appreciate knowing the "why" behind the "what." Thanks much.