It's very possible that he got these when he was younger. For all I know he is a Yankee fan or Jeter fan and went on a run only targeting Jeter rookie cards. Everybody does something different with their collection.
I also wouldn't doubt that over the years he just hoarded as many as he could knowing how popular Jeter is, the team he played for, and the value of that card knowing it would go up over time, with the intent to sell in the future.
While the card will continue to go up in value over time, I think this is likely the last big burst you're going to see for some time, between now and HOF induction day. He likely sold the lesser condition ones early just to get going and now that the vote happened, put the highly graded cards out there for the big money acquisition.
I also wouldn't doubt that over the years he just hoarded as many as he could knowing how popular Jeter is, the team he played for, and the value of that card knowing it would go up over time, with the intent to sell in the future.
While the card will continue to go up in value over time, I think this is likely the last big burst you're going to see for some time, between now and HOF induction day. He likely sold the lesser condition ones early just to get going and now that the vote happened, put the highly graded cards out there for the big money acquisition.