Q about man who sold the boat (major spoilers)

Elvis' friend was clearly in on the meat harvesting thing, since we saw him in the video with the island's former doctor. He sent people to the island regularly to be used as food.

But the zombie locked in Elvis and Tweeter's boat seemed intentional to me. How else could the man have missed the fact that a zombie was in the hold? Is there a reason why he might have done this, that's gone over my head?

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"Gentlemen, you can't fight in here! This is the War Room!"--Pres. Merkin Muffley