Black has all their pieces defending the weakness on c6, far away from their king, and therefore White initiates a dangerous attack.
It is very typical to get rid of the doubled pawns at the first chance that we have. By doing that, we are not only improving our structure but also opening the position for our bishops.
Black naturally wants to capture with the bishop if possible.
12...dxc4? naturally taking back would lead to doubled pawns once again.
12...dxc4? naturally taking back would lead to doubled pawns once again.
and finally Black eliminates the doubled pawns next move. The position is quite dangerous for White since the two bishops are extremely dangerous along the a6-f1 and b6-g1 diagonals.