> Shorts have the potential to lose a lot of money if the stock goes up.
Not just a lot, but an *unpredictable* amount. It isn't just that you can lose money if things don't go your way. That's always true with investments, especially ones that are famous for having a lot of price-motion, like stocks. But a short position is special because the amount you can lose is unbounded, and this makes it risky to hold *even* as part of a diverse portfolio. If you invest 5% of your portfolio in a normal stock, and it tanks, you can lose up to 5% of your portfolio. But if you put 5% of your investment portfolio into a short position, and the stock increases to e.g. 200 times its former value, you could lose 1000% of your investment portfolio, which is probably significantly more than your entire net worth. The 200x increase isn't especially likely, but the possibility of something like that happening is always there with a short position.
The Trump stock is more unlikely than most to have a very very large increase, because the company doesn't do any significant R&D and is already valued at a relatively high level. But it's probably *more* likely than the average stock to have a more moderate increase that would make a short position, not completely ruinous, but decidedly uncomfortable. All it would take would be for a couple more of Trump's political enemies to file yet more lawsuits against him (which does *not* seem unlikely), and his popularity would probably go up again (like it has done the last half dozen times that happened), and the stock price would probably increase as a result. So honestly, I think shorting the Trump stock is probably a somewhat more manageable risk (as part of a diverse portfolio) than a typical short position (but that's not a high bar) but also less likely to pay off. It's not an investment strategy I would particularly recommend.
I expect people are going "This is overvalued; if its bubble pops while I have it shorted, I make money." And that's true, as far as it goes, but that doesn't mean it's a good idea.