What is sane about that, if they already own more than they could ever reasonably spend for their enjoyment?
Same thing that is sane about a paperclip optimiser making paperclips, or a mammal improving its sexual attractiveness
Number go up
Neuron activation
It's called capitalism. Whether that is sane, or individual self-interest without empathy is a trait of sociopaths, i'll leave up to psychologists and historians to debate.
The scorpion shrugged, and did a little jig on the drownings frog's back.
"I could not help myself. It is my nature."
Then they both sank into the muddy waters of the swiftly flowing river.
I don't see any reason why they cannot simultaneously be malicious criminals and insane.
Sane isn't defined by ... take as much as you possibly can and assume there are no consequences to anything.
And that is why we hand testicular cancer a drivers license and voting rights.