The Lord of Light willed it so that Stannis Baratheon may never have a male heir.
But in two marriages -- one to his beloved from House Vaeleris, and another to a religious zealot of House Florent -- two daughters were born. Unlike a son, they would never be able to rule Dragonstone in the way the laws of men dictate.
His eldest, Rhaena Baratheon, would need to marry and Stannis determined there were no men more honourable than those of House Stark.
Biding his time after his failed rebellion, Balon Greyjoy learns that his erstwhile heir is returning home at the new Lord of Winterfell's behest, seeking terms for an alliance between the Iron Islands and the newly crowned King in the North.
In one timeline, with his decision weighed upon his sense of pride and his sense of pragmatism, Balon's pride won out.
But what if he made a different choice?