This weakens e4 for the rest of the game.

Exploiting the protected square. White's next move makes things worse, but his game was difficult anyway.

With strong pressure.

By attacking the d6-pawn White prepares 2 Bf3 in order to swap bishops, after which the weaknesses on d5 and d6 will become easier to exploit.

4...f5 seems preferable, preventing Ne4.

Since the plan of tripling the major pieces would leave the c4-pawn in danger, Karpov prefers to open a new front on the kingside.

Thanks to his strong passed pawn and more active pieces, White is better.

Getting rid of the bad bishop and reducing White's control over the light squares, in particular c4.

After 2.Bxb5?! axb5 the weak pawn on c2 and the entry square on c4 are more relevant factors than the doubled b-pawns.