It wasn't Kuina because he wanted to be the best before he met her, but she made his resolve even more sturdy. It seems Oda didn't start Zoro backstory at the beginning or just gave us a moment in his life. Similar to Sanji. We didn't get major part of his flashback. We didn't even get major part of Luffy flashback until later on. What do you guys think is the reason Zoro initially wanted to be the strongest swordsman.