Because picking both you’ll end up with at least 1000 dollars. If you pick only the million-or-nothing box, you risk not getting anything.
The prediction aspect just messes with your mind in that you want to use it to your advantage but you really can’t, as past events don’t guarantee future outcomes. So only by believing (I would call it irrationally) that the entity put money in it because it expected you to pick it, you would win it.
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