I think you misinterpreted the image. It's currency traders with a pile of currency on a table.

Somali currency is not worth much, but it was never worth much. What is interesting is that the government basically going away did not lead to worthless currency.

The bottom would fall out of bitcoin if X% of the users decided they didn't want to use bitcoin anymore. If that's the same X% as the dollar, that's far fewer people, and thus correspondingly more likely.