What did he possibly have to gain from this?
The city was lost. Euron had lost his improbable aiming skills. He could have just run but instead he tried to fight and kill a non aggressive Jaime. Why?
What did he possibly have to gain from this?
The city was lost. Euron had lost his improbable aiming skills. He could have just run but instead he tried to fight and kill a non aggressive Jaime. Why?
A few reasons:
If he plans to wed the Queen to make himself King, he can't have her lovers hanging around. Especially one that has historically been the father of all her children.
Last time he left King's Landing, it was to fight with Daenerys against the Night King. This is a treachery that shouldn't go unpunished. Now Euron may be miscalculating on this point, since I'm not sure Cersei would have actually been thrilled to have Jaime cut down, but he's still a traitor.
Obviously Euron thinks highly of himself, and loves for others to as well. If he beat Jaime frickin' Lannister, he'd be famous for it. He's the Kingslayer, after all, and well known to be one of the best fighters around. Sure, he may be down a hand, but details get left out over time. As it is, nobody will ever know what happened in that fight, but if he had won handily, then he'd tell the story his own way.
Jaime is one-handed, and Euron sees himself as a badass. There's no way he thought he was going to lose this fight.
This is Euron. He loves to fight, and he's never really liked Jaime anyway. Even disregarding the rest, why not have it out with him here and now?