One of the confusing aspects of the Christian situation is that - although sin is a consequence of choice, of free agency - humans on earth nonetheless seem to have been set-up to fail - to sin.
Having been set-up to fall, to sin; then we have had to be saved.
But it all seems a bizarre roundabout rigmarole...
Why did God the Father not simply create a situation when we didn't sin in the first place?
(By making humans more wise and self-controlled, and setting us down in a better situation.)
Why would our Heavenly Father do such a thing to us?
Clearly we are not intended to sin - clearly the way we ought to live is the way Christ lived - which is that Christ was subject to all the temptations, but always resisted them.
That is what we would ideally do - and by feeling but not yielding to temptations, we would learn everything there is to learn from our mortal lives - but come to no harm.
So that is how we should behave - so why didn't God make us that way?
One simple answer is that He could not make us that way.
Since we really do have free agency, we really are autonomous beings.
There is that within us which is independent in origin from God - we are not wholly created: there is a tiny flame individual to each of us alone, which precedes our creation.
A grown-up cannot be made as such - a grown-up is the result of a process of growing-up.
The child is made: the adult is a product of 'education'.
Therefore we must learn, must develop, must grow from here to there.
God has taken that tiny individual flame, which existed but was unaware and could do nothing, and made us his children - given us consciousness, agency and indeed given us almost everything.
But we are still simple, weak, undeveloped beings.
There is a gap to be bridged between what we are, and what God hopes we may become - but we necessarily and only become it with our own consent and desire.
Since we are not now like God, and since it is God's will (His wish, His loving yearning) that we become more like him (by theosis, by spiritual progression) this is what necessitates the roundabout rigmarole of mortal life on earth.
We need to be educated by mortal life, and we are as wise and self-controlled as God could make us at this stage in our development - which is not very wise, and poorly self-controlled.
Therefore mortal life is an education by trial and error - and the error is inevitable for creatures like us.
So we have been placed here, where we learn by temptation, however we will (by choice, but inevitably - given our weakness) fail to resist temptation and will sin.
Therefore we have provision for repentance and we have been saved by Christ's atonement.
We get the 'educational benefits' of earthly mortal life - and are saved from the consequences (on condition of repentance).
(Bear in mind also that this scheme was set-up by God - but nobody was compelled to comply with it: all mortal humans are volunteers for this life on earth.)
And there is no other way, or rather no better way, that this could be done - no way that God to achieve the theosis, the spiritual progression which he desires for us without going through a real process of trial and error.
Education (which necessarily involves free agents) just is slow and roundabout and contains repetitions and apparent redundancies - hence the rigmarole of our lives here and now.