Sacrificial offering?
A bigger fish told him to alter the email, he would not do it without direction. He provided that name, more evidence to convict a higher up. Typical way they do these investigations.
For one thing, it opens the DOJ/FBI to a whole boatload of civil lawsuits from the victims of this malfeasance. An explicit admission of guilt will remove any indemnification for the agency and the individuals involved.
Wow! We have a token charge. Time to wrap up everything, it’s over! We found the one low level person who is completely responsible for everything. Ok, now we can have the weekend off. Wrapped this up before the election. Good job everyone! Back to our day job.