I think a lot of it is just column inches and hot takes for engagement. I've argued that it shouldn't be a points trophy in the past, and still believe the Norris should go to the best all-around defenseman instead of the best scorer from the back. I probably argued here that Vlasic should've gotten votes prior to ~2014-15.
But this is literally a performance we haven't seen in a generation, and anybody watching more than clips on YouTube from this Sharks season could tell you that Karlsson isn't just the straw that stirs the drink, he's the whole goddamn glass. Adam Fox, Cale Makar, Miro Heiskanen, Hampus Lindholm? All great players having great seasons. Karlsson is having a season that only five players in the history of the league have bested, and none of those guys are on the list. Arguing that he isn't the player who has "demonstrated the most all-round ability" because he's -21 on a team that's overall -82 is disingenuous at best.