It's not you, it's the weird way that difficulty conditions work.
ES assumed that designers will give the player more bonuses (extra units, extra upgrades etc.) on easier settings. The harder the level, the fewer of those bonus triggers get activated. Maybe ES did not foresee that designers might have the idea of making enemies stronger on harder difficulty levels.
The Problem: The chosen difficulty level in triggers does not only get activated if the player plays in exactly that same difficulty level. It also gets activated if the player plays in an easier mode.
I hope I'm doing this the right way round, otherwise I'll go back and edit it later:
On Hardest: Only Hardest should go off.
On Hard: Hard and Hardest get activated.
On Moderate: Moderate, Hard, Hardest get activated.
On Easy: Easy, Moderate, Hard, Hardest get activated.
On Easiest: Fireworks! Trigger chaos! Message chit-chat! (All five difficulties get discovered at once.)
I hope ES won't apply this logic to their editor in AoM... Ingo