It needs a trigger otherwise there will be plenty of bots to "arbitrage" on the said "price mismatch". Whenever there is capital control, there will be "black

It needs a trigger otherwise there will be plenty of bots to "arbitrage" on the said "price mismatch". Whenever there is capital control, there will be "black market". The question is about depth and whether enough depth to influence the price everywhere. The scenario you describe is a liquidation crisis for cryptocurrencies at large (everyone runs to Fiat). This certainly can happen, but needs a equivalent size of a trigger.