I believe that the Trump Organisation is actually a Closely Held Corporation, and as such there are some things that aren't the same as normal LLCs, including Majority Shareholder Liability. This means that because Trump has a majority holding in the company, and can basically have the company do whatever he likes, he also has liability for the company.
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Why would you believe that? No one else does. There are no shares of a Trump corporation trading on any exchanges. It's an LLC that owns a lot of other LLCs and other properties.
https://en.wikipedia.org/wiki/The_Trump_Organization
https://www.investopedia.com/updates/donald-trump-companies/