Indifference

Four years and 10,000 children later, Obama had yet to accomplish anything in Syria.  50 000 more people have died since the chemical agreement, and now Assad is starving cities as a weapon. 
Putin now attacks Crimea because he knows the indifference which resides in the white house and Europe.
As someone who was born long after world war two, I never understood how Hitler happened?  How did the world get to the point where such a human was in control? It seems indifference is the key. 
Indifference in leaders allows a bully to exist, and now Putin is bullying the world.