I've been working on queries and requested fulls these past few weeks.
One thing I've noticed is that writers frequently offer up a lot of backstory or "whys" in the first few pages. Sometimes that's a good thing.
Most often though it is not.
Readers don't need to know everything at the start.
It's better, often, if they don't.
NOT knowing creates tension. That's a GOOD thing.
Consider if your novel was a chess board.
Does the game begin when you set all the pieces in the right place?
It starts when someone MOVES.
And if you're not familiar with the rules of chess, you don't know why the knight moves in an L-pattern, or the rook stops cold when another piece is in the way.
Not knowing creates tension.
Remember your reader isn't wondering why you're doing things, they're just following the story.
It's only when they CAN'T follow the story that they start wondering what's going on.
Sometimes I hear "my beta readers said we needed to know X or Y."
That's not good advice.
You WANT your reader to wonder about things. That's called tension.
Part of your development as a writer is being able to distinguish between what information your readers need to follow the story, and what we don't need in order to build tension.