I don't know why you're assuming that he's just sending out emails and finding receptive people on the other end. In my opinion that's the least likely scenario considering the range and calibre of his guests. You don't get to cold-email Eric Schmidt as a relatively unknown person and have him be the guest on the 8th episode of your newly started podcast. You don't get Elon Musk, Ray Dalio, Jack Dorsey, Roger Penrose and the creator of just about every big programming language just by cold emailing.