This is yet another reason to reject KYC. It's also crazy SSN of the customers got leaked since AFAIK it's very important data for those who live in US.
If we take into account that ATMs are usually the most expensive way of selling/buying cryptocurrencies, I wonder why all these users agreed to such KYC and did not use some CEX where they should still do KYC, but the fees would be many times less?
In addition, CEX usually have better exchange rate. Anyway, i would guess the reason probably similar why people use ATM rather than mobile/internet banking, familiarity with or strong preferences towards ATM.
Also, considering that the company behind everything went bankrupt, is it possible that they (or one of their employees) actually sold that database?
That seems possible, but i think it's also possible the employee don't bother dispose the server securely.