8.Nd5 is threatening both the b4 bishop and breaking the kingside pawns by B/Nxf6, so Black has to do something about it.
At the Capablanca era 7...Bxc3 was considered almost obligatory, but later 7...Ne7 was established as at least equally good- white has no good way to take advantage of Black's doubled f-pawns.
I am reading Chess Fundamentals by Capablanca.
Example 17 has this game.
Now, at the move Bg5 Capablanca wrote:
"A very powerful move, which brings us to the middle-game stage, as there is already in view a combination to win quickly by Nd5. This threat makes it impossible for Black to continue the same course. (There is a long analysis showing that Black should lose if he also plays Bg4.) He is now forced to play 7...Bxc3, as experience has shown, thus bringing up to notice three things."
Which combination wins quickly for white by playing Nd5?