I think the statement is quietly brutal. They make it clear that the decision has been made on the basis of fact, and not on a whim, when they say 'neither results nor performances reached the levels we believe the team was capable of'. And they presumably have the data to back that up. Maybe he was Montague's choice.
The final parting shot of 'We are highly optimistic about the club's future' could almost have 'now he's gone' in brackets after it.