Hacked after purchasing legit Nitro

Yesterday afternoon Discord notified me that there was a promotion to pay Nitro for 1 month and they give you another month. I proceeded to the purchase on my PC and everything went smoothly.

Now at dawn when I get up I realize that someone entered my account and began to buy several monthly suscriptions of NITRO since my credit card was recorded in the system. However, thank goodness all but 2 transactions (like 30) were declined. I've already changed my password, reported the card, activated 2FA, and reported it to Discord support.

I don't have any viruses on my PC or gone to weird places. I have no idea how this could have happened. Anyone ever happened something similar?

Thank you