The main reason people feel jealous is, that the compare all day long things with each other, that is what thinking mainly does.
The problem is that we even start to compare when there is nothing to compare. It makes no sense to compare apples and pears. They are in different classes, what classes they ever may be.
When one of my friends build a thriving business, it doesn't mean I can do that or that I must be successful too.
My friend is a different individual than I, has a different history, different abilities.
When I compare the two of us further, thinking turns into something that Krishnamurti called violence. Because the ideal is always or most of the times higher then I.
Jealousy is part of our egocentric world view.
Egocentricity makes us to look down on other too, on the basis of comparison.
But often people who are suffering, who are failing in life start to make problems. All sort of problems, drinking, environmental pollution, violence ...
It may not that we are directly harmed by them, but in some way their energy effects us too, one way or the other.
Thanks for the nice article.