Best doesn't equal most valuable.
Lets take a look at something
NHL Trophies
The Hart Memorial Trophy is an annual award given to the player judged to be the most valuable to his team. The winner is selected in a poll of the Professional Hockey Writers' Association in all NHL cities at the end of the regular season.
The Ted Lindsay Award (formerly Lester B. Pearson Award) is presented annually to the "most outstanding player" in the NHL as voted by fellow members of the NHLPA.
It is obvious that the two trophies are not meant to be rewarded based on the exact same thing otherwise the only difference from what is said about them would be who votes on them.
We clearly see that voters for the Hart don't see most valuable meaning the best. I agree with them as do other people.
Hall 93 points while 2nd best on his team had 52 points totaling a 41 point difference.
McDavid 108 points while 2nd best on his team had 70 points totaling a 38 point difference.
So we see that McDavid didn't have the biggest point difference from a teammate in the NHL.
McDavid helping Oilers win some more regular season games but not enough to make the playoffs isn't as valuable as Hall helping the Devils win some more regular season games that resulted in making the playoffs.