Why does the act of Hamlet jumping into the grave evoke pity ? and why does it not ?

In my mind, I tend to think that it does evoke pity. 
Particularly because it is one of the first times that Hamlet shows his emotion publicly
and it happens that he is expressing terrible grief for this girl he loved who was
destroyed by the intrigue and the absurd maneuvers of Polonius and Claudius and the
court.

I think the argument could be made that it does not
evoke pity given that Hamlet has been so constantly back and forth and it is difficult
to trust his emotion, even when it appears to be genuine and powerful enough to bring
him to act in public rather than rant in private.