Guy was pretending to be scammed hoping someone would feel sorry for him and send first. Then he scams.
I think it was probably actually to build trust. He was hoping that by being a "victim" of multiple scams he was hoping that the eventual buyer would believe him when he said he sent the bitcoin.
The problem is that anyone who has enough trading history to have a good amount of trust will know to verify the receipt of funds prior to sending funds of their own