Henry winter summed it up well on Twitter imo -

Sarri leaves #cfc with head fairly high. EL winner, 3rd place, EFL Cup final. But failed to connect with fans, often uninspiring football, record PL defeat, overlooked youth until late, restricted Kante, predictable subs, rarely a Plan B. Likeable bloke but too stubborn. 1/2

Really a year too early for Lampard but worth a gamble. Will re-connect with #cfc fans, give youth a chance (important with transfer ban & talisman Hazard gone), brings buzz, influential Morris, entertaining style, Cech mate, decent work at DCFC (who’ll be loath to lose him) 2/2