Why did the artist of the above painting place all the figures in rows in the picture plane?

I believe the artist did this, in order to demonstrate a story or event. all the people are lined up, instead of just one or two, because they are depicting a event. By looking at peoples expressions, mannerisms actions etc. it may give a hint to the events the art is centered around or based off of, something similar to propaganda demonstrating bias images in a similar manner

Explanation:

the answer of "what has three legs but never walks" is a yard stick. this answer can be found at