Do you have a Nintendo Switch? Did you also have a Nintendo 3DS or Wii U? If you answered yes to both of those questions, there's a possibility your Nintendo Switch account was one of "about 160,000" breaches that Nintendo announced on Friday morning.
https://www.businessinsider.com/nintendo-switch-account-breach-impact-2020-4
https://www.businessinsider.com/nintendo-switch-account-breach-impact-2020-4