They probably spent all their savings on the down payment, as approximately everyone on the planet who wants a place to live but can't pay for it all out-of-pocket does?
Investment shenanigans excluded, if you have enough savings to pay off your mortgage in case you lose your job, there's no point in getting a mortgage in the first place.
Investment shenanigans excluded, if you have enough savings to pay off your mortgage in case you lose your job, there's no point in getting a mortgage in the first place.