With regards the "What really is the point of somebody hoarding this much wealth?" question, I've been thinking a lot about this recently, as the billionaires accrue more influence than ever before. And I think that's the keyword - 'influence'. After a point, wealth doesn't buy you more things, it buys you power, which is seductive. It goes far beyond making your family comfortable and doing right by your company, employees and shareholders; it becomes a means to lever the world. Yes, some of this drive is about being apart from the real world and possibly an element of personal sociopathy (corporations are famously sociopathic entities, too, which probably rubs off on the C-suite execs), but hedonistic adaptation (we're very good at getting used to things, even vast wealth) and wanting to change the world are (I imagine) very addictive. I imagine it even goes some way to assuaging the embarrassment of The Leader of the Free World calling you his AI Expert...sorry, 'SI' Expert.
And it really doesn't help that all these tech bro billionaires think Ayn Rand was a good writer with some fine ideas.
Related: the market cap of the stock market is basically a conversion factor between currency (for daily purchases) and power (being in charge of all the world's companies). When the market crashes after an election, we shouldn't think of it as "$3T of wealth wiped out", it should be "power gap between normal people and billionaires decreases" (it takes fewer normal people to buy a billionaire's position).