This is really an instructive position. Play was focused on restricting the activity of one of Black’s minor pieces, a key middle game strategy that is often seen at grandmaster level. We have following position after Black’s last move 19…Rd8:
Q: How would you continue from here with white pieces?
20. b5! Ne5?!
Other options are also just good for White, for example:
a) 20…Ne7 21.c6
a1)21…Bc8 22.Bc4 Nd5 23.cxd7 23.Rxd7 24.Qa2 Rd8 25.Nd4 and white enjoys pressing position.
a2)21…Ba8 22.Bc4 Nc8 23.Qa2 Nb6 24.Rd1 with fantastic position.;
b) 20…Nb8 is just bad because of 21.Qa5 Bxf3 22.Bxf3 Qe5 23.Rc1 and Black has a very poor knight.
21.Nxe5 Qxe5 22.c6 Bc8
22…Ba8 23.Rd1 d5 24.Qd4 Qxd4 25.exd4 produces a position where Black’s bishop is even worse than on c8 which was what happened in the actual game.
23…d6 24.Qa5 d5 25.Qa1 Qxa1 26.Rxa1 gives White a winning position.
24.Qd4! Qxd4 25.exd4 Kf8 26.f4!
Now Black can’t achieve e5 without a significant loss of material which means his light square bishop is very bad. Carlsen went on win after few more moves.