They did plan ahead. They took the money above the cost of the loans as profit and handed it off to the executives and investors, and used the equity built up by paying down the loan to help get the loan to buy the next property. And, as another said, around and around again.
You see, they know it's a game of musical chairs, and that at some point the music's going to stop. Their plan is that when that happens the company is left without a seat, but the people behind the company can walk away with all the money and none of the liability for the loans (thank you corporate veil). The ones who loaned them the money can pick over the penniless corpse of the company and try to sell it's assets (mainly the buildings) for whatever they can get.
Ideally the people behind the property company are the only ones who have the free cash to buy those buildings, which they can use the value of to get loans to buy more buildings, starting another round of the game. The smart move would be for the banks to put language in the loans saying that the loans have first call on the income from the building and that if the property company defaults on the loan the bank can go after the owners and executives of the property company personally for the balance up to the total income received from the building.