The Minister is appointed and in actual fact he doesn't even need to be an elected member of Irish Parliment. He can be appointed by Irish Prime Minister to Irish Senate
I don't think this adequately explains the position; it's extremely rare for a Senator, let alone an appointed Senator, to serve as a Minister. And it's irrelevant in the current context.
The more apt observation is that aviation policy is set collectively by Government. In this instance, after many years of (as another poster said) protecting Shannon at all costs, policy is now promoting the longer-term development of Dublin in the context of the national economy. Even at that, the policy document is peppered with the superfluous addition of "and Shannon" to many statements that really only apply to Dublin.
But, at least, the objective of the policy is reasonably clear.
The Regulator seems to be just assessing the short-term commercial interests of EI and FR. This is a good political intervention, the kind that rarely happens.