There was no data leak on chess.com.
There are services and databases of compromised accounts. We monitor them. For example, according to https://haveibeenpwned.com/ , your credentials leaked from at least 2 websites:
Gravatar and MyFitnessPal
I won't share screenshots here. Please use the site above or contact chess.com Support Team using Help -> Ask a Question.
Why did the site not tell us about this?