Let's not forget Mark McCormack in the major department. As Palmer's agent, he suggested to Palmer that he play in the Open in 1960, when Palmer was off to England on an endorsement trip at the same time. A slight rearrangement of the schedule allowed Palmer to qualify (!) and then almost win.
The Drummer may have written about it, but McCormack, the marketing genius, really created the modern grand slam. Funny thing was, he was a native Chicagoan and even played in the Western Amateur once upon a time. But he forgot about the Western Open, a major from 1899 to you-pick-the-date, when it came to exploiting Palmer's heroics.