Why don't you answer your own question for a change and follow through with the logical conclusions you must face instead of burying your head in the sand of generalities that ignores the details.
Here are some truths to think on:
1. We are made in the image and likeness of God. Gen1:27
2. There is an innate corruption in the flesh. Rom.7:23
3. We are of the flesh. Gen.5:3 Jn.3:6
4. Which makes us slaves to sin. Rom.7:14
5. Nos.1&3 set up a conflict that is made apparent when God manifests Himself to man. Rom.7:15-20
6. The creation, prophets, Torah and the work of God the Son and Spirit all point to God's existence and man's situation in relation to Him. Matt.11:13 Jn.1:9-10 Jn.16:8 Rom.1:21
7. God comes to us with grace and truth. Jn.1:14
Once you comprehend the above, Rom.1:21 answers your question as to how the mind becomes darkened (they reject the truth shown) and Jn.1:14 explains why not all minds become totally corrupt and desperately wicked (there are those who do not reject the truth shown).
There is a whole lot more that could be said, but it has been said ad nauseum.
So, in your words? Thanks for the discussion.
grace and peace.