What they usually come back is with is something along the lines of there was a mistake and their relocation company accidentally sent their childcare deposit and ______ something important and could you please wire the excess amount back to them immediately and they will pay for the wire.

Being military and relocated frequently it never made sense but I can see how someone might do it in the sense that we care about kids and if the money was for the child's physical to leave the country or copies of child's documents or whatever we think of a child suffering if we don't do it. Even if they pay for the wire they will still get enough money from the scam. The urgency blamed on the child's needs is so it gets done before the bank catches on.