The concept of wealth fundamentally depends on the society its created in.
If I am the last person on earth, i effectively "own" the entire earth, but it means nothing.
Same for a man staving to death on top of a mountain of gold.
Which makes this billionaire New Zealand apocalypse compound trend all the more ridiculous, if society collapses, being a billionaire is going to mean absolutely nothing, you would think the money would be better spent ensuring that doesn't happen in the first place