Crosby has a much better reputation than Ovechkin, which is a factor here. The nice thing about Crosby is that he's never had a down year. Can't really say that with Ovechkin.
2017-2018 Crosby season wasn't great (top 10 in scoring - great for anyone else, but for Crosby it's 'meh'), but he bounced back with a strong playoffs. Hart runner up in 3 of the past 4 seasons outside of that. Obviously this current season he won't be a hart finalist - but that's because he had a big injury and missed so many games. On a per game basis, he's still doing really well.
Ovechkin hasn't been a top 10 scorer any of the past 5 seasons, including this current season. His highest hart trophy placement is a 6th place in that stretch.
Crosby benefits a much greater reputation as a player in terms of hockey ability today, than Ovechkin. Age helps a lot too - since he's 2 years younger.
I didn't take injuries into account - not sure we should. It'd be one thing if a player had a lingering injury that might affect future play - but that's not the case with Malkin. But sure - he's more likely than most to miss games again next year.
I'm not saying OV should be ahead of Crosby, I'm saying the reasons are similar (even if you want to say Crosby is better).
Going back 5 years really doesn't mean anything for today. 3 is more relevant and even that might be too far.
Who cares if he hasn't been top 10 in pts? Hart finishes of 6,7,9,12 and he would have been top 10 again this season so he's been recognized as a top 10 player despite his pt totals. Also for comparison, Crosby in a healthy season missed the top 15 literally 2 years ago and would have missed the top 30 this year. So who really has the "down year" in the last couple of years?
Age has nothing to do with who is a better player today. Crosby's big saving grace is always his playoffs but OV has been better than him in the last 2 as well (I know Crosby is better for career but that doesn't mean much for today).
Anyways, I'm not saying OV should have been above Crosby. Just saying the arguments for Crosby also apply to OV: champion, track record, still ~top 10 in the regular season, but can turn it up in the playoffs, etc.