Sometimes when people cry and we don’t understand why, it is because there is something they know about what is happening, either big picture or little picture, that we don’t know about...and maybe if we knew what he knows, we might cry too. It is a possibility.
A simplistic example is when I was a child I didn’t understand why people cry at weddings. Now, as an older person with more experiences and knowledge, it now makes sense to me that people cry at weddings.