Please help me understand the thoughts of people who actually want (for example) $20 Billion Dollars.
I'd like to accelerate the spread of knowledge.
With $20,000,000,000 I could open a "Flying Spaghetti" Monster temple in every city and beside every large church, and educate people about brainwashing while feeding them free pasta - the body of my lord.
https://www.venganza.org/
With US$20 billion and your own religion you can also afford to do lots more marketing and get even more money and solve world hunger with free pasta.
One colander at a time.
If you lived in Zimbabwe before their currency went out of existence you would have wanted more than $20 billion. Since a $100 Trillion banknote was worth around US$300 (When issued) Now they are a novelty sold on eBay.
At least with $20 billion dollars you could actually buy a small item. $5 million you could staple together (if you had lower denominations) and use it as a notepad. (Although you may not be able to afford the staple)
Taking your wallet was painful.
But the answer of why someone would want $20 billion also depends on where you rank on the Selfish / Selfless scale.
On one side would be private golf course, helicopters, mansions and power.
On the other side of the scale would be solving the worlds problems and power to make those changes.
So the short answer would be : Power, control and things. Things for your self or things for others. With a preference for US$
The other answer could be - if you were Satoshi - to create a revolutionary crypto currency that will change the world and leave that value stored in bitcoin wallets untouched so that there is confidence, scarcity of supply and growth (and change the world).