That's because their goaltending has been shiiiite. Not a Kings fan / haven't seen many games but fancy stats bear out the fact that the Kings are positive in all the ES categories that most ppl pay attention to (corsi, fenwick, shots%, xgf%, scf%, even hdcf%). Columbus is net negative in all those categories and bottom 5 in the league (ie truly terrible) in most. I can throw numbers at you if you want but you can look them up yourself on NST:
For a more top level metric, CBJ is allowing 35.0 shots per game (3rd worst in the league), Kings are allowing 28.4 shots against per game (5th best). If you really want to argue that LA is a worse defensive team than Columbus, then by all means good luck... but then I'd ask you not to use arguments which basically only show how bad your goalies have been (for the record, Kings have 3rd worst sv% in the league at 89.88% despite better than average overall defensive metrics).
Imo that's why the trade for Joonas wasn't the worst idea, imagine what you could do with a league average goalie or maybe one who is even better than that
EDIT: included NST link