Pepe is quick, for a CB he can really shift.
A high line needs defenders who are comfortable themselves/capable of jumping forward to win the ball before it moves through.
That's why the likes of Thiago Silva are so renown, quick across the ground to make sure they get to the ball first or the player who will receive it can't move with it.
Lescott is slow and unsure of himself outside of the box and struggles massively.
When Richards plays at CB, his physical attributes are what makes him put in the performances he does. He isn't Maldini when it comes to defending so relies on his speed and power to make sure he either gets the ball first or the player receiving the ball can't get away from him because then he will struggle.
Kompany has the blend of both, T.Silva the same, Pepe imo the same, Varane and Sakho too.