I've worked in a bank's collection department for 3 years and from my experience, these things do happen. Not all the time of course, but it does.
Banks usually have a way of scoring the financial behaviour of their customer i.e: debits, credits, payments for any form of borrowing etc. When a customer pose a future risk, as the bank, we'd take all the money that we can to minimize loss. Any payment is always welcomed of course, but by cancelling it (in this case the card), they've removed future risks from yourself.
At the end of the day, do not take it personally. The bank has tonnes of rules, procedures adand SOPs that they follow and your account happened to be in their review and the outcome was unfavourable to you.