I'm kind of surprised, as I thought Kucherov would get it with his late-season scoring push. But, in this case, I think the voters actually got it right (they got it wrong in 2018 when MacKinnon didn't win then).
They're basically equal, and the Hart could have gone to either guy. I do think MacKinnon was slightly better, though:
There's nothing wrong with getting empty-net points, of course, but Kucherov had A LOT this season. In fact, he had more than any player in history (was it 14?), So, you'd think, such a player must have played on a really top team with all sorts of leads late in the third-period while they beating up the competition. But... Tampa wasn't a great team. They were 13th overall. They were good, not great. So, it's odd that a player on such a club would have so many EN points. Like, in how many games exactly did Tampa even face an empty net? 14? It seems like every single time they had an empty-net, Kucherov was getting that point.
So, fair play, those are good points. But how many EN points did MacKinnon have? (I don't know.) If you take away the EN points from each, it's likely that the tiny difference in point production is now negligible, or even in MacKinnon's favor. And in ES points, they're basically exactly even.
So, I don't think there's any offensive advantage to Kucherov.
In terms of who tilted the ice more, I think you have go with MacKinnon. Obviously, Colorado was the better team overall and you'd expect better ES results from their players, but even so MacKinnon's +35 was easily the best on his team (and way better than Kucherov, but that's team contextual).
So, I'm okay with it. I mean, if you take the Hart definition literally, Kucherov probably was "more valuable to his team", but by that literal definition, then the real Hart winner was probably a good player on a really bad, non-playoff team (i.e., nobody takes it completely literally -- nor should they).
So, I'm okay with it.
(And by the way, I don't like MacKinnon much, and I quite like Kucherov.)