Why did Rod Steiger want the role of Michael Corleone?

This story intrigues me

According to “The Godfather” author Mario Puzo in his 1972 memoir “The Godfather Papers,”. The Producers were contacted by the talent agency represented by Rod Steiger. and said that he wanted to audition. The producer was perfectly willing to consider Steiger for the role of Don Vito Corleone, and began to arrange the details of the actor's screen test. However, the Agency clarified that Rod wanted to auditioned for the role of Michael Corleone. The Studio and Albert Ruddy found this request Bizarre as Rod was 45 years old and was a year younger than Marlon Brando, so Ruddy politely turned down the request.