Clearly the system by which "grandma" owns a small part of a criminal organization is flawed.

Whether criminal liability needs to flow to individual owners I don't know, but I'm sure someone has done the thinking here about how to make this less insane.

Large shareholders are very different than grandma owning a few shares or even a few hundred shares. If criminal risk was priced into the stock, our society would look very different.

if LLCs didn't exist, clearly the stock market would operate differently

would Enron have been Enron if it wasn't an LLC?

I certainly do. The stock market would have fewer bubbles if risks were born by the owners!