Given the real money involved, keeping it online with this flaw in place isn’t an option.
Just like you don't shut down your store if someone stole some merchandise or how credit cards just factor fraud into the fees.
There are businesses where if you suffer a theft, you shut everything down and run a stocktake. For example, an arms dealer. And there are times credit card providers shut down - because there is a known vulnerability, and they have to immediately mitigate, or lose their insurance.