A coupled entry pays the same for each horse, 1 and 1A, regardless of order of finish. It is as if they are one horse for pay outs. 1A won the race paying for win, place and show. The 1 horse was going to pay the same WPS regardless of where it finished. It finished second so all win and place money went to the coupled entry.
Exotics (exacta, quinela, trifecta, superfecta) in this case go to the third place horse since the coupled entry cannot be separated in such bets. You could not bet a 1/1A exacta because it's the same entry. And since that entry took win and place money the exacta defers to the show horse.