They have sold 1 starter in Salah, Szczney was a LOANED PLAYER, they did not sell him. They decided to bank on their younger and quite talented goalie Alisson to be starter now, makes sense.
Rudiger was BACKUP and ROTATIONAL player, good explosive defensive talent, but not a starter. The CB starter besides Manolas was Fazio, thats why you saw Rudiger as RB alot to give him playing time (when both RBs were injured). They litterally signed 2 backup players to essentially replace Rudigers versatility basically, in Moreno and Karsdrop.
Paredes was 100 procent backup, and again I repeat, I seen both players enough, Paredes is more of a nifty passer, but Pellegrini, his direct replacement is better then him IMO. So whats the loss in getting a better player who costs a mere 1/3rd of what they got for Paredes?