I’m glad that you see it so simply and fairly because that is exactly what it is not.
He thanked the man for not investigating him while firing him for investigating something he was convinced was worth jailing Hillary over.
He fired him for investigating Hillary? Why? Is it because he didn’t enough on Hillary to satisfy Trump?
Well, the only reasons we have been given are the ones in relevant documents. We have the official announcement which says he was fired over Emailghazi–it’s unclear if it was because he acted unprofessionally or because he didn’t act unprofessionally enough. And we have an internal memo which says Trump had decided to fire Comey a while ago and asked the AG’s office to come up with a pretext, which was presumably later decided to be Emailgazi. Other than that, all you have is speculation. Certainly a lot of that speculation seems more credible than the official announcement.