It is probably a part of a larger antiquities investigation.
The article says.... Robert A. Jones, special agent in charge of the Indianapolis FBI office, would not say at a news conference specifically why the investigation was initiated, but he did say the FBI had information about Miller's collection and acted on it by deploying its art crime team......
Meaning they had actionable information to acquire a warrant.
Perhaps he was offering some for sale or trade, perhaps he contacted someone in an ongoing black market sting to purchase under the table items. Perhaps an agent posing as a seller was invited in to his home and saw illegal items. Perhaps a friend of the guy realized some of the items were illegal.
Perhaps he was buying pilfered items from a museums storage. Perhaps someone busted for black market antiquities turned on the guy.
Perhaps items were tracked through customs to his house.
there are a million legit ways the FBI could have keyed in on this guy. So he is 91.... big fucking deal.
This is a big money, highly corrupt market that operates largely under the table. It is rampant in europe and the middle east, and there are teams of people who's life work involves tracking and recovering illegal items.
Hell- a single purchase from egypt is more than enough to attract the eyes of the egyptian watchdogs.
My Mom used to work for the egyptian consulate, and the lions share of her work was dealing with customs issues on exports from egypt... they watch it like a hawk, their laws have teeth, and they have the cooperation of the US in tracking and finding illegal goods.
This seems completely above board and logical to me.