There are a number of reasons an account might get killed off, but there's also more than one type of account you may be talking about, and different types of suspension for different reasons.
You've said Trello, so it's likely to be an Atlassian account, but we'll need to know if it is. (How do you log into Trello - is it via the account you are using here to post your question? Or is it another account?)
I would want to go to my.atlassian.com and see what the state of the suspended account is, then contact https://trello.com/contact with the details. They may not be horrendously fast to respond, but that's the only way you are guaranteed to get a response.
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