If this rather melodramatic piece were redone today you might get a psychological explanation for Rudolph Valentino's behavior. Quite simply put Rudy is a sex addict, title and all.
Cobra has Valentino cast as a man with a title going back many generations, but he's cash poor and he has a compulsion to bed every woman he meets. You can imagine that such behavior has left him with few friends. But he gets a lifeline from America in the form of vacationing millionaire Casson Ferguson offering him a job in New York City where he's got a certain expertise in antiques and that's Ferguson's business.
It doesn't take long for Rudy to start returning to his old ways. It means tragedy for one woman he's involved with. In the end he does an honorable thing.
The Cobra did not do all that well as the movie going public liked to see Valentino in costume dramas. There is a small flashback sequence where you see him as one of his ancestors. Maybe had the whole film been set in the 15th century it might have worked better.
As it is The Cobra is second tier Valentino.