The entire point of this post is asking what happens to KYC when the business goes bust and there is no employees and if they delete accounts do they delete KYC information. Alot of exchanges going bust and I'm curious
Businesses are often required to keep documents a certain amount of years even after going out of operation, though to what extend will vary from country to country.
Regardless of that, even if a defunct company deletes your KYC data, it doesn't necessarily mean that it is gone. It could still be stored in a government database somewhere or other third parties -- sometimes KYC gets outsourced to other companies so these might still have copies. And of course there's always the possibility of a data breach.
Beyond that since they did do business in a lot of countries and they went though the process of getting licensed in those countries they more then likely are following those rules.
If country 'X' says all records must be saved for 5 years then anyone who registered from that country has their data sitting someplace for 5 years.
If country 'Y' says all records must be saved for 7 years then anyone who registered from that country has their data sitting someplace for 7 years.
As others have pointed out there are 3rd party businesses who do this for you. Somewhere buried in the T&C there was probably something about this.
-Dave