Well, Catelyn broke an oath she made to the Gods (to love Jon as her own if he lived through an illness during infancy), and then kidnapped Tyrion, which got Ned a spear in his leg, making him too weak to fight the Lannisters and protect Robert from getting “attacked” by a boar...

Unclear leader. Bitter convention battle. Failure to come together. Splintering party. Opportunities to fight the real threat are lost while infighting distracts. The other candidate pulls ahead.