Of interest is that the mortgage holder did not require that the taxes be included in the monthly payments. Brings up more questions. Tax sale and the mortgage holder loses?
As a rule of thumb, if you take out an 80% loan to value (LTV) meaning you borrow no more than 80% of the value of the property, the lender will not require the taxes included in the monthly payment. The idea being you will make your tax payments when you have more skin in the game.
Given the loan was likely a standard construction with a roll over into the perm. The loan was likely closer to a 65% LTV and would have qualified at the time of not requiring the taxes to be collected monthly.
As for the exposure, the lender would step in and pay the taxes and save its outstanding loan.