Normal MMR and Ranked MMR are separate, so what you play against in ranked has no real correlation of who you play against in normals.
Additionally, the restrictions are a bit more lax. E.G. As a high gold player is more likely to get matched with a lower silver player in a normal than in a ranked game.
I wouldn't take too much stock in normal games and the competition in them as a measure of personal skill. Most of the time when I play in my normal games I play in my worse roles to practice or try new builds and strategies. Sometimes I will do a game to warm up prior ranked. I can safely say if you play against someone who is significantly higher rank than you in a normal and you "own them" they probably aren't really trying or are playing a champion they don't normally play etc. I have played and beaten Diamond players in my normals, but they are playing a role they never play or a champion they never play or are trying some odd build. I don't put hardly any stock in it, just like if I get beat by a silver player in the mid lane I don't think much of it since I rarely play mid.