Firstly Chelsea are playing West Brom, you'd expect them
too win.
Secondly, what's been wrong with West Broms football? They like to play the ball along the ground, patient build up. Only thing lacking is a clinical finish/striker.
You said yourself West Brom have been poor.
Their defending has been slack (obviously because its 5-0) and they can't seem to find that clinical finish. They looked all over the place when Drogba scored the 5th.