Well, to understand jealousy you have to understand his twin brother...GREED. The reason a lot of people are jealous is because they want what others have, they aren't satisfied with what they have. They have to justify to themselves why they don't have what you have, and the easiest way for them to do so is to assume you didn't get it fairly. That way they don't feel their lacking is due to their own short comings. It's the same with class envy. People without are jealous of those that have and so they assume that the other person must have gained it through illegal or unethical methods so that they don't have to face the fact that either 1. they are lazy, 2. aren't as skilled/intelligent/gifted as the other person, 3. made poor choices, 4. made good choices but aren't satisfied with the consequences of their choices (in other words, they may have a job they enjoy and are good at but it's NEVER going to pay the kind of money they apparently really desire).
Up until the end of this year I used to hunt a piece of land which was covered in deer. We hunted about 400 acres in a very rural area. We were surrounded by literally thousands of acres that others had access to hunt. Two hunt clubs and a couple of unofficial groups of hunters hunted the properties around us. This place has 100's of deer, I've seen 100 in one day. Every piece of land holds some deer. You can literally be standing by your truck on a field eating lunch and talking and have deer run you over. The two hunt clubs use dogs but we and the other "unofficial" groups don't. I can't tell you how many conflicts we've had, or the other groups have had. Seems hundreds of deer aren't enough for everyone. I've had stands tossed out of trees, guys trying to start fights and game wardens called on us. Which is funny considering we are the only ones not illegally hunting on the roads. The hunt club hates us because we shoot deer from the woods while they run around in their trucks chasing the dogs. Human nature. It sucks some times.