Your comparison between that and the Pens adding Malkin and Staal is gibberish.
Between 18-19 and 19-10 it was basically the same players, the same coach and the same scheme - mere Months apart. You think they all just flipped a switch and they all sucked when Crosby was there but they were all magically great without him a few Months later? That is unlikely.
Nevermind that Crosby was given huge amounts of credit for defensive assignments that he didn’t have. 34 of the homers in the media claimed Sidney Crosby was the best defensive forward in all of hockey that season - better than Bergeron, Couturier, Barkov, Stone, etc. That is a le bad hot take.
The Canadian media exaggerations were was obvious in real time. Crosby's offense wasn't good enough to be supporting their claims so they pumped up a myth of defense to compensate. I wasn't remotely the only person to see it at the time.
Then in a fun turn of events, the theory that Crosby "carried the team" (despite them being a recent Stanley Cup winner) got put to the test. It got blown out of the water on the basis of a .714 winning percentage in a pretty reasonable sample size.