Note the use of "Trump" and "he" throughout this article.
Donald Trump did not enter into these contracts. A legal entity developed and partly owned by Trump entered into the contracts. The company had Trump's name, but there were no personal guarantees or, apparently, any payment security (payment bond, L/C, etc). Anyone entering into a contract with this legal entity was obliged to do a bit of "due diligence" to satisfy itself that it was signing on with a company that had the wherewithal to meet its debts.
Construction subcontractors typically insist on either milestone or progress payments, which are intended to ensure that they will never be very far under water if the project goes belly up or if the project owner does not pay. Also, non-payment during construction is grounds for suspending the work - without penalty, for those with the balls to do so. Finally, these companies apparently were willing to sign contracts that waived their statutory right to file a mechanic's lien - something that should only be done on rare occasions when there is no question of payment. Had they not signed away their lien rights their bargaining position would have been much better when the casino failed to pay.
In this case, it was a very speculative venture, created on the assumption that there would be enough people willing to pay premium prices for food, lodgings, and services, when compared to other gambling establishments nearby. The contractors mentioned in the article made very poor business decisions and did not exercise very good project management during the course of the work.
Trump develops projects all over the world, many of which are very speculative in nature. In most cases they are successful, but sometimes the projects fail. There is no comparison with a lifetime politician (or wife of a politician) who basically does nothing, and can basically never fail to do it.