Odd that Mr. Oldman didn't research the family?
Mr. Oldman seems to be a very intelligent, shrewd and successful businessman. One who covers all of his bases and has never been caught in any of his scams. So why, considering he doesn't trust Claire and her behavior and all of the red flags, would he trust the info Fred was giving him about the family instead of having one of his assistants research the family and their background? If he had, what would he have found? The real Claire Ibbetson was the dwarf in the bar, and the villa was her family's, so maybe if he had researched it he would have found exactly what Fred was telling him?
Terriers always smell like warm, buttered toast.