Feedback on Book Order

I am currently considering writing what I originally thought would be book 2 of my trilogy as book 1. However, this would mean a majority of the information and secrets of the current book 1 would no longer be a surprise to readers. Including the fates of some characters.

I know if “book 2” gets big enough readers will be more open to a prequel but that’s if it gets big…

I know my info is a bit vague but any feedback is appreciated