This proverb is a reference to Claudius killing his brother. The poison (the axe) was only the cause of old Hamlet's (the tree) death. He still remembered that his brother killed him and he came back as a ghost to tell his son to avenge him.
”The Loneliest People Are the Kindest. The Saddest People Smile the Brightest. The Most Damaged People Are the Wisest. All Because They Do Not Wish to See Anyone Else Suffer the Way They Do” ~ Loneliness Quote.the damaged part of this quote is so true!