Its not even her lack of brains, its just dumb that she's thrust into a leadership spot out of nowhere of which she's completely unqualified for. She doesn't know a thing about politics, about leading and about managing a faction, much less an entire kingdom. It just felt like bad writing in a game that really doesn't have many instances of it.
Its not like they were drowning in candidates, but the entire thing felt rushed and needed a hell of a lot more time in the oven. Ala Mihgo needed its own Xpac, just like Ishgard got, if they wanted the story they told to feel anything more than disjointed and rushed. I know that Ala Mihgans are extremely low on everyone's "care" list when you stack them up against Snow Elves and Dragons or Not-Japanese samurai and ninja, but don't make them half of an expansion if you don't have the space or the passion to make them feel like less than throwaways.
Doesn't help that their former king was an absolute moron, but hey.