Are they grappling because they don't "believe it happened" or that "it didn't happen that way"?
Or is it just innate human curiosity trying to make sense of something they can't quite wrap their brain around?
I think it is something else, not intellectual, but emotional. They want to avoid shame.
If you say you believe in the creation account of Genesis nowadays, the world will mock you for it, and for those that are of the world, and value the praise of the world more than the praise of God, they will feel foolish and ashamed because of that mockery. So, only those who are able to put aside their worldly pride are going to want to endure that.
Well if Christians don't believe God is the uncreated Creator of all, then that is quite an issue.
Also if they have issues with "it didn't happen that way" see my previous comments. God was being short and sweet with the Creation account. The focus of the OT and NT is the plan and fulfillment of the redemption of mankind.
We are inquistive creatures made in God's image and likeness. That rules out mankind coming from other primates.