Expectations are so high now, so a blip or performance dip is a disaster. It is for CFC business incorporated too as well as post -Abramovich fans.
Underperformers are quickly despatched. Can be a double edged sword though to react so quickly - eg Hiddink, Salah, de Bruyne - as every player has performance troughs. However, the Abramovich hire and fire model seems to have worked pretty well since 2004