[Discussion] Why and How did Naruto be strong and intelligent, because....

[Champ]

He's still dumb and because he was given Kurama

 

[Mr Hiru]

At the beginning, Naruto always insist that Kakashi to train him.
Kakashi had given Naruto one important advise, and his "wind" element.
By using this "Multiple Shadow Clone Technique" ;
Then with this jutsu, Naruto will able to learn much faster.
Also, Bee told both A & Tsunade, that Naruto will learn better in 'active' scenario.

Discussion..........................

Wrong. Naruto is not intelligent. He is philosophically wise, he is clever in battle, he has good improvisation skills, but he is not intelligent.

Kakashi's advice only let Naruto learn faster because his mind is not as fast as his body, remember that Naruto is from those people who learns with the body. Repeating excersises is what lets him do the learning job faster.

So even if your answer is right, your question is wrong.