Because Nxd5 is a bad move! 6.Bd5 Nxd5? 7.exd5, displacing the knight and also threatening d4. 6.Bc4 is good according to Stockfish
I understood, thank you for explications.
So my next question is : Why 6.Bc3 ? (2nd theorical move after 5. ... Ke7) Now 6. ... Na5 exchenge Knigth against Bishop and the bishop doesn't win tempo in d5 square !
I'd rather develop, equalize, then embark on an attack.
Reponse of Stockfish for this position is :
7. c3 Nxb3
8. Qxb3 Qg8 (I don't understand this move for black)
9. Qc2 h6
10. Nf3 Qh7 (I don't understand this move for black)
Stockfish evaluation : 1.1 for white.
My opinion : I thing loose light squares bishop against a pawn is poor compensation for white in italian game !
I play 6...d6 instead of 6...Na5
Yes but my question is :
What is the advantage to play 6.Bb3 instead 6.Bd5 for exemple ?