On the other hand.... Lets say its true. Lets say that we are only seeing evidence of the poorly performing businesses, and Stubby McBonespurs actually has hidden businesses that have more than enough income to cover his losses.
That isn't exactly a sign of a very good businessman. Usually, when you have a large organization with multiple branches, the company will cut out the poorly-performing ones to concentrate on the more profitable areas. (Unless of course they need to stay open for strategic reasons...) If Trump is actually keeping (for example) golf courses open despite them operating at a significant loss, that is the sign of a bad businessman.
It depends on what's causing the losses.
If the businesses themselves are running at a loss, receipts running well behind expenses then that's one thing and you're right, a good businessperson would either address the losses or dispose of the loss-making part of the business.
OTOH if the businesses are running at a loss because they're paying a huge fee to another Trump business to licence the use of the Trump name and/or are carrying a huge debt load because Trump has lumped them with the loans he took out to buy them in the first place and/or are carrying loans belonging to other Trump businesses or Donald Trump himself. This is the kind of approach the Glazers used when they bought Manchester United. They bought the club with loans and then transferred the debt to the club.