We are blaming the guy for committing a hate crime with the purpose of nothing other than to antagonize a group of people and incite chaos. So yes, that's what he is being blamed for. The people who killed him are to blame for murdering him and will be charged accordingly. But it is important to state that the guy who went to a peaceful mosque to burn their holy book in front of them is a trash human being.
If you keep poking somebody and you get hit back, you are not blameless in the ordeal. If you opress a group of people and they lash out, you are not blameless and there are 2 sides to the problem. Of course nobody should resort to violence. But if people get insulted right to their face, spat on, pushed into a corner (not just talking about this specific scenario obviously), then eventually somebody is going to react in a bad way. Don't be a cnut in the first place and antagonize for no reason is the right way to fix this issue, because there will always be nut jobs who will react with violence.