Anyone who knows photography can tell me why this photo won the prize, and where is his subject? What's special about his composition and content? thank you

The main reason why this photo won the prize is its news and timeliness, not its artistry.

Its composition has no aesthetic feeling and can be said to be useless, but because of this, it shows the suddenness of the incident and the haste of the photographer. The content of the picture highlights the various human performances and authenticity of the injured and rescuers at the first time after the terrorist attack.