Liverpool has had every bad break so far this year (including a goal line clearance just now). The first two games were mostly down to bad bounces (they dominated on xG in both), and the injuries have really added up. A hysterical fanbase full of newly minted plastics demanding that Liverpool win every trophy ever has only added to the negativity.
And some older players have really started to look tired this year. Henderson isn't his usually steady presence, Fabinho is unusually shaky, and Firmino is a shadow of his former self. Even Van Dijk has had a few moments of madness. The youngsters like Jones and Elliott have promise, but aren't quite there yet (and Jones is one of the multitude of injuries). Add FSG trying to turn a profit to overcome the losses of Covid (net spend is almost 0 so far), and pickings are thin. Also, no stability at the back again, with three different starting CB pairings in three games so far.
With a ManU side still smarting from the whoopings last year, and it was no surprise that Klopp was trying to talk them up in his pre-match. They were always going to work hard today, and an early goal is far from ideal.