It's really hard to grasp. Maybe this way: it's more millions than most people have dollars.

That's a great way to put it. Makes my brain hurt.

Correction: investors from all over the globe value the shares in Bezos' possession at 172B.

These investors could also arbitrarily declare these shares as worthless (theoretically), and Bezos' net worth would crater to only consist of his leftover cash and physical assets in his possession - real estate, art, cars, etc.

That's an irresponsible use of the word "theoretically". What actual theory would have them do that? You're describing a coordination problem of absurd proportions and you haven't even proposed a shared motive.

It like saying, "This specific aspect of society could change if a potency-majority were fully committed to the idea that it should be changed in that way."

You're absolutely right. I don't try to pretend that it would be possible in the slightest. Just that stock wealth is a societal, and thus arbitrary, construct, unlike, say, gold and precious gems, which have intrinsic value across time, space, and cultures.

At some point stock is as intrinsically valuable as gold, when it has legal support and billions of people buying and selling it. I have no interest in gold and I never will afaict.

"would crater to only consist of his leftover cash and physical assets in his possession - real estate, art, cars, etc."

That is still much more than most people will possess in their entire lifetime.