If they're good friends off of the ice, which I don't question, then Panarin should've had more empathy for what Kucherov was going through. This is like if your buddy is torn up over breaking up with his girlfriend and you crack a huge smile and try to high five him because, now, the two of you can hang out more, like you used to. You would never do that. Instead, you'd feel bad for him and console him, since that's what friends do. Maybe later, you gently spin it as a positive, but not just moments after and while he's still on the ledge.
Now, friends should also be expected to be happy for one another, but any good gesture that Kucherov was willing to extend to his friend probably went out the door when he saw Panarin's over the top gesture and smile. I don't blame Kucherov one bit for not appreciating it. It was only a minute after likely the most crushing disappointment of his career (if not life) and his friend was celebrating it with him. I'd be miffed, as well.