DPR must have known that the blackmailer and hitman were the same person. He paid him 150,000 to go away.
I thought the same thing. He not only got the blackmailer to go away, but he sent a message that "If you fuck with me, I am willing to pay $150,000 to have you killed." If he didn't do that, what's to stop the blackmailer from coming back a couple months later demanding more money?
This way, the blackmailer walks away with $150k in bitcoin and thinks, "Wow, I got lucky to outsmart DPR this time. Next time, he may hire someone real to kill me."
I think DPR was smart enough to know he was being scammed, and also smart enough to manipulate the scammer to receive this message.