That most likely had to do with your purchase history pattern. Good banks will notice abnormal patterns and freeze your card/account until you approve the charges. Overseas charges are a pretty large red flag, particularly if you simultaneously have charges in your home area. It also depends how the card was run by this company for this second verification... Virtual Terminal vs. a normal checkout flow can sometimes be treated as a "Card Not Present" charge, which can appear more risky to your bank/card company.

Not foolproof, but is a help. Also... another reason to use a credit card for all online purchases... it's not your money, and almost always will be refunded in full if disputed (at least in the US). Bank cards/debit cards are your money, and you might have a fight on your hands with your bank if it's a large enough charge.