The reason why Liverpool's form dropped this much should be some mental problems. Of course they faced some injuries and had many missing players as a result. Diaz was one of them and we all know how important he is for the team now. He is trying to do his best to fill Mane's place in the team. His performance so far has already been impressive.
However I don't think injury is not the main reason for this. Because they had really bad games in which they defended their opponents very poorly. Klopp needs to help the players improve their motivation. This squad are capable of doing anything they want. They just need some push.
Indeed, injuries were not the main reason for Liverpool's downturn at the start of this season, but the loss of important players in the squad greatly affected the rhythm of the game, but now Liverpool have returned to their best form, Liverpool are now sixth in the standings, I am very confident Liverpool will be able to get up and come back played well after the world cup event, because Luis Diaz had recovered from injury.