I thought a bankruptcy procedure is about distributing the remaining assets to creditors in an orderly and fair way. How can this prevent him from losing his assets?
You're mostly right, but there's probably laws governing exactly what assets are redistributed to the creditors. Maybe he is able to stash some assets with his wife or in some complex offshore setup. You'd need lawyers to say. Or the bankruptcy court even.
There was recently a high court judgment in Norway with Alexander Vik who refused to pay for a large currency trade. He tried for years not to pay and even moved his values over to his family, but at the end he lost in court and the money was claimed from his relatives.
He might have put a subset of his assets in a foundation, which is not included in bankruptcy (as he no longer owns the assets -- the foundation does).
Foundations however, have no owners (generally only beneficiaries), so they often cannot be held liable for the debts of the (original) founders.