Unintended Apple Pay subscription purchase on Headway website

I went to the headway website, I wanted to buy a subscription for 3 months. I chose the payment method via Apple Pay, paid for everything via Face id. After I signed up for a subscription, windows with different additional subscriptions began to pop up where the opt-out button was small and right under the subscribe button, I missed and clicked subscribe for some additional subscription and when I bought some before the subscription, which I accidentally clicked on, there was no face ID and the money was instantly debited from the card. Why did this happen, and I didn't need to confirm the payment again, and the money was debited instantly

[Re-Titled by Moderator]