Scammed Again?

About a year ago, I got scammed for more than $2,000. I managed to get the money back from the merchant and only had foreign exchange conversion losses. At the time, Commonwealth Bank said they couldn't do anything because I had approved the transaction. This month, I found a round $50 transaction on our credit card from Seenenergy/Post Melbourne Australia. Neither I nor Moominmama recognized this transaction so I raised a dispute online. Almost instantly Commonwealth Bank refunded the $50! I wonder what is the difference between these two cases. I suppose that I did not actually click anything to authorize this transaction? Maybe it is because this is a credit card rather than debit? Or both? Our credit cards have been cancelled and we need to wait for new cards.