This is one of the main plans in these kinds of structures, opening the diagonal for the dark-squared bishop. Now the white bishops directly target the black king, and White's attack will be unstoppable.
17...Nxc4 looks super strong for Black, but White is winning after the precise 18.Qe4 g6 19.Bxc4 Qxc4 20.Qe5! f6 21.Qe6+ Rf7 22.Rc1
followed by d6.
followed by d6.
The black king is completely naked in front of so many attacking white pieces.