Because those men dug through concrete rubble with their bare hands, with no care for their own skin or anything but to recover bodies—living or dead—of loved ones. It’s the human tribal instinct at work, the survival instinct. And they happened to get to the baby before oxygen was depleted.
Also, no heavy object fell directly on the baby. The child appeared unhurt, the way it was scrubbing at its eyes and screaming, like any normal healthy child would in that situation. If facilities are available, it should be taken to the hospital for a full checkup. It will be coughing up dust for a long time to come.
But there must be others in that rubble. Babies that age are never alone. The video cuts the minute the baby is completely retrieved. Did they find the hand of its dead mother at that point? Or a dead sister?