In Superman: The Movie (1978), Lex Luthor plans to become wealthy by (Spoiler alert but you've had forty years to see the movie so I'm not hiding it) buying desert real estate, then nuking the San Andreas fault and causing the western half of California to collapse into the ocean, converting his land to oceanfront property.
He seeks to ensure the success of his plan by (a) launching a second missile towards Hackensack, NJ, thus ensuring that at least one missile would hit its target and (b) hanging a lump of Kryptonite around Superman's neck.
My question is this: What if Superman had gone after the California missile first? The Hackensack missile would have hit, but under the plan as described, Luthor would not have profited from that. He would have made himself into a mass murderer for no gain. His choice of Hackensack rather than, say, Gotham or Metropolis would seem to increase that risk, as Hackensack is a relatively small town as compared to the entire coastal population of the state of California. The second missile seems most likely to create a way for his plan to fail.
To be clear, I am not asking what the screenwriter's motivation was for including the second missile (I assume it was an unused bridge to events in the sequel); I'm asking what Luthor's motivation was.