Are unregenerate people in that state because of something they did, or were they just born that way?
They were born that way. Their sin is just a symptom of their state. It is evidence of their lost condition. They are evil trees and bear fruit that is evidence of that evil.
Look at this verse:
Romans 5:12 KJV
12 Wherefore, as by one man sin entered into the world, and death by sin; and so death passed upon all men, for (as evidenced by the fact) that all have sinned:
So sin is merely proof that we inherited the fallen nature of Adam. It is not "judgment" as much as it is simply evidence. It is an obvious observation of the fallen state of men.
You did not have to sin the sin of Adam's rebellion to be fallen:
Romans 5:14 KJV
14 Nevertheless death reigned from Adam to Moses, even over them that had not sinned after the similitude of Adam's transgression, who is the figure of him that was to come.
So rationalize salvation in the same light. We are saved by no virtue of our own righteousness. Just as we were made (as in transformed into) sinners by the action of one man (Adam), so too you are saved (transformed into righteous) by the action of one "man", Jesus.
After the original sin of Adam, you could not do anything to regenerate yourself to a righteous nature. Hopeless. Even those "good" things are filthy rags.
Isaiah 64:6 KJV
6 But we are all as an unclean thing, and all our righteousnesses are as filthy rags; and we all do fade as a leaf; and our iniquities, like the wind, have taken us away.
What does an unregenerate person have to do to maintain his nature? Nothing.
What does a regenerate person have to do to maintain their nature?
I like the verses that follow in Romans:
Romans 5:15-17 KJV
15 But not as the offence, so also is the free gift. For if through the offence of one many be dead, much more the grace of God, and the gift by grace, which is by one man, Jesus Christ, hath abounded unto many.
16 And not as it was by one that sinned, so is the gift: for the judgment was by one to condemnation, but the free gift is of many offences unto justification.
17 For if by one man's offence death reigned by one; much more they which receive abundance of grace and of the gift of righteousness shall reign in life by one, Jesus Christ.)
The phrase "much more" is key here. It is saying that the grace of God is better at keeping people saved under grace than the condemnation of sin is at keeping people lost.
How lost are the lost? They are hopelessly lost—no possibility of escape.
The text says we are "much more" saved than the lost are lost. They are hopelessly lost, we are more abundantly saved than that.
God is better at keeping us saved than the devil is at keeping the unregenerate lost.
