A bit late to the party, and haven't read through every comment, so apologies if this is was already stated opinion.
In many (if not most) cases excess wealth is a byproduct of capitalizing on others labor in an unfair way. There was (not so long ago) a time when excess income over a certain amount (say a million) was taxed anywhere from 60-90%. This high level of taxation mixed with the victories of the labor movement standardized that upper management and ownership made around 10X max what their average laborer did. That number has now swelled to 100X-1000X the average salary and with minimum wage (US) basically the same for the last 20+ years.
Beyond having more than you could ever use and depriving a portion to those below you; the systems of capital seem as much about cleaving society into separate castes and classes (as much as anything.) We've had the ability to bring the world out of poverty and hunger for a long time now and instead we've managed to perpetuate myths about those less fortunate being a burden around societies neck. The poor are raised to look at the poorer as impediments to their ascendancy and the idea of base universal standards as rights for humanity have stalled and are largely no longer talked about. Capital has done everything it can to divide people with hate and drain money from the bottom, while maintaining the expectation for never ending growth of markets and resources. This is unsustainable and will eventually lead to rifts that will break governments and societies around the world. Probably faster than most of us think or are willing to accept.
In America so many of us think that we're always one lucky break from rising away from those like us. So as secret millionaires we tacitly approve in the hopes of living better than the rest. Legitimately though, to be rich (from means other than luck (EDIT, see bottom)) will come down to how little you care for exploiting others. If you can take more from those around you and feel less about it, then you could be the next millionaire. And it is this difference in ethics and mentality (possibly psychopathy) that leads to being rich and doing fucked up shit.
I've worked for very wealthy people and they are masters at disguising themselves as adequate people. They are usually very charismatic and can say all the right things without being found out for a very long time. Being wealthy makes people view you as exceptional. You must have been smarter, worked harder, more godly and/or more worthy. As such, people almost always give you the benefit of the doubt much more than they would a regular person. And the rich are exceptionally good at wearing that trust just to the point of breaking for as long as they can. From my experience they are largely on cocaine or prescription stimulants, so that they're always "on point." They buy excessively, without thought and will throw even costly unopened things away. They become bored with life and begin sexual abusing those in proximity to them. These tastes will continue to become more extreme and degrading so that they can feel more power and hurt others more. Hurting people, without consequence, is a great way to assure ones self of how untouchable they really are. They come to enjoy these things and have no care for those they hurt unless it affects them in some meaningful way. They can make up stories that allow them to feel fine about this when it's clear they've done horrific things (DARVO behaviors) and thus will likely never feel any lasting remorse for even the worst of things.
This last part is again from personal experience, but it largely matches over a number of people and I see no difference in the actions of the vast majority of the wealthy. Surely there are some wealthy people who not all of these things apply to, but they are exceptions and not the rule.
We could point to so many things that make the world awful but the overly rich and powerful are a nearly singular point that if toppled could right so many wrongs. Humanity needs a second bill of rights and even beyond a maximum wage, the majority of excess wealth and holdings needs to be taken back and used to fix humanity's course.
All of that certainly isn't going to be happening though, so I look forward to spending the horrifying future with the rest of you poors!
Edit: @Aesthesiaphilia pointed out that inheritance is the largest means of wealth transfer and they are absolutely right. Previously the notated EDIT portion said "to be rich (from means other than luck or some inheritance)" and I've edited out the inheritance portion because you could inherit a million dollars randomly or 500 million. The amount doesn't matter as the impediments to generational transfer of wealth between elites has been substantially weakened even recently and it very much folds into the myth of the self made millionaire/billionaire, which is not supported by reality.