Medicaid payback after death

My brother recently passed away from cancer and was on Medicaid so he could get treatment. His ex-wife and children were notified that they had to repay Medicaid. He only had a car, truck and camper, no estate. The car has been sold to pay off the car loan and the truck and camper were given to his ex-wife because she paid personally for his gas and transportation to get to his treatments. So really he had nothing when he passed away. Why would Medicaid want repayment from his ex-wife and children?