To me, the rub is that people apply what I call “linear thinking” to a non-linear and transcendent God, who is not trapped by time and space. He is already all-knowing of our future, yet still allows people free will to choose.
To the natural mind, this sounds crazy to say one can choose Salvation by the Gospel of Grace as a personal choice; while also being Divinely Ordained by Foreknowledge… Much like quantum physics, it is even more insane to try and hold the same natural principles of logic of our reasoning to the Lord God, who is not trapped by physical nor a linear existence.
Remember, within the scripture, time, space, and even the will of God by prayer, have been altered. An example of this is with David concerning Saul, (1 Samuel 23:7–13) which allowed the Lord to alter the course of what was predestined to bring Glory and worship to God – himself.
In short, just like in the physical world where we are governed by the law of gravity, the spiritual world is governed by the law of faith – rather than our intellectual theology.