My best thought on the conundrum of God creating Adam and Eve to fail is this:
God can do anything at all (if we suppose that God exists and created the world). So that begs the question of why would God create people?
We cannot do anything for God that he could not do himself other than engage in a voluntary relationship. The only thing an omnipotent God could not do would be to coerce such a relationship and have it continue to be voluntary.
If we hold that to be true, then the problem of sin is due to God wanting to have a relationship with humanity and being unwilling to take volition away from people. The tree in the garden existed, in part, so that humanity could have a choice.
I also think the tree was given so that humanity would eventually know good and evil (i.e. God wants us to know stuff, not be stupid). But the prohibition against eating from the tree was a temporal one (i.e. don't eat this yet, you're not quite ready).
That's my $0.02 (and my $50,000 in student loans) talking.