If Liverpool managed to maintain their form, they could have put a great fight against City for the title now. They led the league for some time but they started struggling too much after that. Of course, the injuries also had a big affect on it but they are still too bad on offense. For example, they could have destroyed Newcastle but missed a lot of opportunities.
Liverpool is having hard time reaching to the European competition, let alone be in fighting chance for city, so they have been doing horrible. They had a 5+ game loss streak I think, and that hasn't happened in years, team looks to be in dissaray and everyone plays like they are done with working so hard.
It could be fatigue reason, it could be injuries, it could basically be any reason we don't know, but they are nowhere near where people assumed they would be. Sure they could have failed to win the title, become second and City would win, that was one of the things expected, and sure maybe one team would play so well that they would shock the world and become second pushing Liverpool to third. But nobody expected Liverpool to be sixth and they are one loss away from being 8th as well, that is seriously shocking and totally unexpected from them.
It looks like they have had a huge focus problem for a long time. Because they have all of their important offense players playing in their games now. But they aren't playing good this season like they used to play. Look at Mane for example. His performance is far worse compared to last season.