For me it isn't that we 'can't enjoy stories where we know the outcome' - dramas are made out of well known stories all the time and are very successful. The People vs OJ Simpson was very good and hugely successful and that focused on events most of the audience were alive for. United 93 had an even shorter lead in time from the story playing out and is still a compelling film.
What I am saying is that staying an open ended episodic series as a prequel is limiting and, I feel, unnecessarily so. Shows, good shows anyway, evolve and grow as writers get new ideas and take the story to different places. Prequels have a defined end, somewhere they have to get to by a certain point with all their ducks in a row. That is what I mean by limiting. Especially as I can't see what the writers would actually gain, creatively, from imposing such a limitation, over choosing a setting that is truly open ended.