The point is to determine the best alternative. Not the best alternative that you can imagine, but the best alternative that is possible. Step one requires temporarily suspending judgement, to consider alternatives outside of your own experience or imagination. Without suspending judgement, outside ideas get filtered.
But, why waste time on outside ideas that are likely nonsense?
See, you already filtered those outside ideas as nonsense.
Suspending judgement is difficult, because it requires you might have to admit you were wrong in your assumptions.
Suspending judgement, temporarily requires that you consider ridiculous alternatives. And if you consider ridiculous alternatives, it frees your mind to generate more ridiculous alternatives in a chain of ideas containing many elements, one of which may actually save the day. Idea fluency.
You may never get to the idea that saves the day without the meanderings of ridiculous alternatives. When we temporarily suspend judgement, it gives us permission to consider things run backward, the front end of one idea connected to the back end of another idea, the ridiculous context of one idea as the crucible for the right idea.