Balon Greyjoy's stupidity

So I've been randomly thinking about Game of Thrones, and started trying to figure out how could Balon Greyjoy really gain independence and not be stupid.
First of all, he chose a bad time to rebell- right after the civil war ended, the realm almost conpletley unified under one king- Robert was popular, the North, the Vale and the Riverlands loyal to him though alliance and friendship as because he's the claimant they helped to install as the king, the Westerlands (Lannisters) allied to him though marriage, the Reach (Tyrells) trying to regain power in the realm and are thus loyal, the Dornish perhaps wrathful but too afraid to do anything... The Ironborn have no chance to win this war.
However, if they declared independence during the civil war, it could have gone differently. Both sides were deep in the war, he could have sent word and told each of them that if they'll give the Ironborn independence he'll support their claim- the Mad King really needed allies and Robert sure as hell didn't want the whole Ironborn army fighting against him. In this time of war, they would perhaps agree, and even if not, he could sttart a second front for both and drain their armies to gain his independence by force.
In the war of the five kings, he has done just that- declared independence while a civil war rages. However, he made a stupid, stupid move and attacked the North- vast, infretile, lands, where most of the 'valuable' things are inland, where the Ironborn are weak. Instead, he could accept Robb's proposal and attacked the Lannisters- they were already busy fighting the Starks and Baratheons, so he could destroy their fleet in  Lannisport and begin conquering the Westerlands, starting by the Lannister sits of Casterly Rock and Lannisport. Meanwhile, Robb would fight in the east (no sacking of Winterfell, Cate doesn't release Jaime since Bran and Rickon are still ok, no Karstark revolt, no red wedding since Robb doesn't need Frey forces) and the Lannister forces would be spread thin- the Ironborn could conquer the Westerlands just like they did with the Riverlands of old (though many revolts would surely arise and Tywin would find a way to restore his lands- that's why Robb would be stupid to do a marriage alliance with Balon, just let him fight for you and then handle his own affairs). Thus, the Ironborn would gain not only assured independence but also fretile lands in the Westerlands. Euron Greyjoy attacking the Reach is smarter, but still not that smart- he can't actually conquer the Reach, the Tyrell army is too big, but Balon could conquer the Westerlands.
What do you think?

You're totally right, Jojen, it's just "Balon Greyjoy´s stupidity" XD. He could obtain his independence if he helped Robb, and with the Iron Fleet all would changed. I think Euron is mad, he wants to conquer all Westeros, and he obviously can't, maybe he's waiting his brother to bring him Daenerys and burn all the people with dragons, but that won't happen, as Victarion wants to take Daenerys for himself, anyway he'll fail too, he's not very clever... Conclusion: Greyjoys morghulis

I think the hit and run tactics they do with their raids is clever. Weakening the forces inland and wearing out the armies. But it is as you say, nothing much to gain from it. No lands no riches, no nothing. The few castles they took was clever. But then again, no true effort to keep it. I find it hard to agree with Balon's sense of strategy if his true wish is to conquer. May Euron take the Salt throne and lead the Iron born to glory!