Well, the fact that they wrote what the Lord wanted them to write comes down to two possibilities, right? Either it is true or not true.
Objectively speaking, if the God described in the bible is real, then He is able to do anything He wants including expressing Himself through His word, and choosing the people He wants to write it down.
So how do we find out if what He says in the bible is true or not? In one of several biblical references, God describes it this way:
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1 Corinthians 2:10-16
"For to us God revealed them through the Spirit; for the Spirit searches all things, even the depths of God. For who among men knows the thoughts of a man except the spirit of the man which is in him? Even so the thoughts of God no one knows except the Spirit of God.
Now we have received, not the spirit of the world, but the Spirit who is from God, so that we may know the things freely given to us by God, which things we also speak, not in words taught by human wisdom, but in those taught by the Spirit, combining spiritual thoughts with spiritual words
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But a natural man does not accept the things of the Spirit of God, for they are foolishness to him; and he cannot understand them, because they are spiritually appraised. But he who is spiritual appraises all things, yet he himself is appraised by no one. For who has known the mind of the Lord, that they will instruct Him? But we have the mind of Christ."
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In short, one comprehends what God wants them to know about anything and everything when God (through the Holy Spirit) reveals it to them.
Attempts at trying to figure out any aspect of the Creator of everything using mere human intellect and emotions alone is futile. It's easier for a single cell amoeba living at the lowest point of the deepest ocean to understand the complexities of a space station.
That's not to say that reason and emotions are unimportant when it comes to the things of God. It's that instead they are secondary at best. The Holy Spirit reveals truth to the real you and me (who are eternal spirits ourselves, living in a body while here on earth according to the bible), and only then can intellect and emotion be brought in to fully embrace it. I mean, the bible literally addresses the point of view you expressed right here:
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1 Corinthians 1:21-24
"For since in the wisdom of God the world through its wisdom did not come to know God, God was well-pleased through the foolishness of the message preached to save those who believe. For indeed Jews ask for signs and Greeks search for wisdom; but we preach Christ crucified, to Jews a stumbling block and to Gentiles foolishness, but to those who are the called, both Jews and Greeks, Christ the power of God and the wisdom of God."
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In this passage, Jews are used as an example of any religious person out there looking for a sign from Him so they have emotional experience as proof to the Lord being real. Conversely, the Greeks are used as an example of the non-religious person out there looking for intellectual evidence as proof to the Lord being real.
This passage says that God chose not do either method. Instead, He chose to save you and me from our sins through what everyone out there believes is foolishness: the sacrifice Jesus dying on the cross for our sins and rising from the dead three days later so we can have eternal life with Him. That's the gospel, a word that means "good news". I expanded on this point
in my first post in this thread.
The wisdom of God, as that passage concludes, can only be ascertained through Jesus Christ. The Holy Spirit is the only one who can reveal that to you. Every other attempt by everyone who has ever lived has failed because the Creator decides how He wants His truth revealed and embraced, not us.