A team resting their key players in league matches they appear on top, is very common to see in matches. Liverpool has an upcoming match to play against Bournemouth in PL. They prefer to win that match rather than playing their key players over the match they seem to have qualified in, round of 16(Champions League).
As Liverpool currently tops the Champions League table, It's gonna be a long time before they have another Champions League match to play. For the time being, their focus will be on mostly Premier League matches because they have a lot of PL matches in the pipeline
The last match of the Champions League was not important for Liverpool. For this reason, Liverpool coach Arne Slot rested the important players of his squad. Even if Liverpool lost in this Champions League match, they would not have faced any problem. Even then, Liverpool's overall performance was excellent in this match as well.
Arne Slot's match strategy is good. So even though Liverpool did not keep important players in their squad, Liverpool was able to perform quite well. But in the end, Liverpool lost the match by 3-2 goals. Even after the defeat, the top spot of the table is still in the possession of Liverpool. I am not worried about this defeat of Liverpool. I believe that Liverpool will perform well in the knockout round matches.