Why did David and his sons sometimes ride mules?
King David's sons lept upon their mules to flee a party spoiled by a fratracide. Mules?
Two Samuel 13:29 Then all the king's sons arose, and every man gat him up upon his mule, and fled.
Later, King David called for his royal mule to transport Solomon to be annointed as the new king of Israel. Royal mule?
Why were mules sometimes preferred to horses? In the flat valleys between ridges, King David's horses pulled chariots.
The terrain upon which people lived around Jerusalem is hilly and strewn with rocks. Mules are more sure-footed, and less likely to injuste their feet, in that terrain than are horses?

Eating Ones Children. In the times before the fall of Jerusalem to Babylon, a mention of eating ones own children was a graphic, effective warning of starvation that could, often did, result in a town that was besieged by its would-be destroyers. In the text below, "Israel" and "Samaria" seem to be synonymous. Though, possibly Samaria referred to the capital of Israel, which nation was distinct from Judah future home of the "Jews."
2 Kings 24: "... king of Syria gathered all his host, and went up, and beseiged Samaria.
2 Kings 25: "And there was a famine ..."
During which, pigeon dung was sold for silver, to be apparently, eaten.
2 Kings 26: "And as the king of Israel was passing upon the wall, there cried a woman within..."
2 Kings 29: "So we boiled my son and did eat him..."
2 Kings 30: "... when the king heard the words of this woman, he rent his clothes."

Rending of Robes.
Why are there instances, in the Old Testament, of people rending their robes?
An early instance of the custom seems to trace back, in stories, at least as far as Jacob rending his garments upon seeing the bloody cloak of his son Joseph. In Genesis 37:34:
"And Jacob rent his clothes and put sackcloth upon his loins, and mourned ..." .
It has been estimated that, before the Industrial Revolution, one shirt would take more than 400 hours of labor: just to spin thread, to weave cloth, to tailor. Fine robes worn of a king might be worth more than one year's labor by a working man. People knew the that royal robes indicated wealth or power. When the king publically tore his robes, he was communicating the seriousness of his distress for his beseiged people.