One of Daenerys first scenes introduces her being bullied by her brother Viserys: "You don't want to wake the dragon, do you." Daenerys seems anxious and afraid. Her sole comfort is found bathing in boiling water too hot for those lacking Targaryen immunity to fire.
Daenerys life story is a history of fire being a liberator and savior in their darkest moments. Whenever Daenerys has problems, fire is where she turns. If Khal Drogo unfortunately dies, all of Daenerys problems disappear by burning everything with fire. She solves nearly all of her life problems with fire, by burning everything. This is a process which repeats throughout Daenerys story until it resembles a life habit.
Another common trend is Daenerys' mercy and kindness being mistaken for weakness. Everyone she meets views her as a naive and weak girl. Everyone tries to take advantage of her. They don't respect her or take her seriously until after she kills them. This is a lesson she is forced to repeat over and over again. Until the end of the story where she's skipping the part where she shows kindness and mercy and fast forwards to the part where she kills people to earn their respect and be taken seriously.
Jon Snows story
Jon Snow's character is an invincible savage on a battlefield. Give him a sword and an enemy to fight and he is unstoppable.
In matters involving peer pressure however he is very weak and caves in. It doesn't take much prompting from his peers for him to assassinate Daenerys. His story is one of an unstoppable warrior with a weak resistance to peer pressure. Who is unable to find a better alternative.
The final attack on king's landing is defined by a moment where Daenerys is piloting Drogo. She hesitates. It looks like she's having an anxiety attack. Fire has been her only comfort from fear and anxiety. But she was supposed to do something different this time and not burn everything.
Somewhere along the line, Daenerys formed a life habit of burning everything with fire. This solved every problem she faced. This is what came naturally to her. And so this is what she did. The only difference was this time was she was murdering people the audience cared about, who may not have deserved it.
In the final analysis, people did not care how many slaves Daenerys freed or how much good she had done in the world. They did not care about how bright of a future Daenerys may have given them as a leader. There is an interesting contrast where the people of king's landing were willing to tolerate Joffrey and Cersei. But unwilling to accept Daenerys.
I for one didn't mind the way the life patterns of characters converged to form a perfect storm of tragedy.