So cloud trail shows the compromised account logging into an EC2 instance every day like normal.
Then service account credentials are used to access user data in S3.
How does cloud trail indicate the compromised credentials were used to access the customer data in S3?
If you ran a cloud trail query that's essentially "Did Alice access user data in S3 ever?" the answer would be "No"
So that brings us back to the question, what is meant by "trust CloudTrail"