He bought it because he wants to make a bunch of money. You said it's a hobby and that they "hope" to make money. There is no "hope. They absolutely KNOW they will come out ahead. He was just waiting for his opportunity.
Was buying the O's his boyhood dream or was that owning the Magna Carta, a signed copy of the Emancipation Proclamation, being Vice Chair at the LIncoln Center for Performing Arts, being on the board at the Smithsonian where he donated 22M towards giant pandas, founding the Carlyle Group, being on the Council of Foreign Relations, advising the President or the 100M+ he's spent on historic preservation? To me, it seems like buying the O's is at the end of a long list of things in his collection, but one that is guaranteed to make money.