Experience.
Most people I come in contact with are polite with good manners.
For example, two weeks ago I was stuck in snow. A few people stopped and helped me out. They didn’t have to.
People are not entirely good, nor entirely evil.
If people were entirely good, no government would be necessary. If they were entirely evil, no government would be possible.
If people were entirely evil, then no government could function, because the people enforcing the laws would be totally corrupt, and would not stop people from killing, raping, and eating their neighbors.
What makes Third World countries stay Third World is they exist in a culture which sanctions corruption, where business cannot happen because you cannot trust the other person to follow their end of the deal, and the courts are corrupt and for sale.
I have a strap in the trunk for just this purpose; but that sure don’t make me good!
I wonder what all those people had in common?