He bankrupted 3 casinos and a number of other businesses at the same time.
The banks couldn’t simply seize the properties so they paid him to keep those businesses running until they could be, which meant Trump, by bankrupting businesses, was being paid tens of millions of dollars a year by the banks he owed money to. The longer he kept going bankrupt, the longer they kept paying him.
He drew loans on those businesses he was never realistically going to be able to pay back, he lied to regulators about it. The plan was for the casinos to fail. It always was.