They were discussing this just yesterday on the Liverpool Reddit and someone posted this video. When Firmino and Mane were his forward partners they worked hard to make Salah the focal point of Liverpool’s attacks. Firmino would drop deep and almost play as a linking attacking midfielder. Manes work ethic on the other wing would free up lots of space for salah to drift from the wing into the striker position to bag the goals.
This season he’s mainly been playing with Nunez, who likes to occupy the central striker area of the pitch himself and use his pace to run in behind defenders. Opposing teams are also targeting Alexander Arnold as the weak defensive link, so Salah has to stay out wide and track back to help out Trent more than previous seasons.
He still has 19 goals and 9 assists this season, but it’s still not what we’re used to seeing from him.