I think they mainly fear that if they pardoned him, it will create a knock on effect leading to even more whistleblowers. People who were on the fence about becoming whistleblowers would see that the repercussions aren’t that severe anymore and hence might take that step.

I’ve also used Tuta. Just gonna point out that some shopping sites didn’t accept my Tuta email. I haven’t used it with financial stuff tho so can’t comment on that.