So there's quite a bit to unpack here. So first thing to note here are the uncanny parallels between Kayle and the Old Testament God. This doesn't to do with a religion so much as it's about creating a mythology. Kayle to Demacia, is what God was to the Israelites, and her story here, is very similar to the book of Exodus. A cruel king ends up invoking the absolute wrath of God in the form of Ten Plagues, and even gets his entire army swallowed up after chasing the Israelites into the Red Sea. In Kayle's story, however, instead of swallowing up a king and his army in water, she does it with fire. It's quite genius because both symbols are more alike than meets the eye.
So with the Old Testament, and this story alike, there are clear differences. First, the Bible is not a literal account of the history of Israel in many cases. If looking at it from a rational point of view, the Old Testament stories were more of metaphysical interpretation of events in time. So they are taken with a grain of salt. Some parts of it are true, others are elements that were added to hammer in a moral. Kayle, on the other hand, is, mostly, an exact recount of the events that unfolded. At the very least, their bios are, as they are told from the perspective's of Kayle and Morgana. The new color story not so much.
This is what I think occurred in the story the Illuminator gave. A wise king made a series of decisions that led his kingdom into disaster. Famine can also be taken as a metaphor for an economic downturn. This wise king, so to speak, drew criticism from his people in a way he hadn't before and so seeing this, the king got full of himself, and fell in love with his own intellect. He lashed out against the criticism, imprisoning people and so on because in his mind, he was the only person fit for the job.
This is an often repeated trope in the Old testament (king sees himself as above God or at least, the ideal of God, leads the kingdom to disaster, and the Israelites repent in return). The king in Kayle's story, by now, has decided that he will do whatever it takes to end the famine, or economic depression. He decides that the ends justify the means and begins killing off anyone who is useless or not working, people represented by the elderly in the story. The king, in doing this of course, shoots himself in the foot in the same way he does so by killing an elderly baker. By killing those who are considered useless, or are not working, he loses the opportunity to mobilize them for a nobler cause and bringing the kingdom out of the rut.
So, having done this, the people of the kingdom object once more, incurring more of the king's wrath. At this point, the king casts aside all moral boundaries and declares outright that it doesn't matter how immoral his actions are because he is saving the kingdom, they should be grateful, he is the wisest person in the land, etc. yadda yadda. Here, Kayle steps in, and absolutely yeets the dude out of existence along with his army. Here's what I think really happened. No one who was innocent died. The only people that died were the ones that truly wished to follow the cruel king. Not even the soldiers who were merely following orders died. Kayle, as mentioned in her bio and stories, has the ability to see malevolence in the hearts of those she judges. Therefor, she is very careful as to who she condemns and can discern the difference between a soldier who truly believed in the king's ways, and one who didn't but was afraid of imprisonment or execution for treason. That's why the kingdom survived with the remaining innocent people.
You might think,"But that's not what the story says." You're right, but this is a myth. It isn't like the bio where it's taken from Kayle's point of view. We know those events happened because Kayle, herself, was witness to them. This story is one that has been passed down by oral tradition, much like the Old Testament stories were longgggg before they were ever written. Stories like that tend to be changed and refined to fit a particular moral. In the case of the Illuminator, the moral in her version of the story was, Fight for those in the home that you love.
But it's important to remember that's only one interpretation of the story. So, here's my interpretation of the story, and yes, my moral is a little different than the Illuminator's. The moral is, Don't Stray from the Path of Righteousness. Vague, but let me explain.
First, it's the same moral of the stories in the Old Testament. It is effectively a lesson to humanity that we tamper with the idea of the individual sanctity of human life at our peril. It is a moral law that no human, or person if you include all the different races, should ever break. By extension, that means arrogance on the part of a king, such that they believe they are above this moral law, inevitably leads to chaos and disaster. Runeterra does not operate under a morally relative standard. This story is proof of it. There are some things that a person should *never* do no matter how powerful they are, no matter even if they are a great wise king. Kayle is the enforcer of this moral law, in the same way God is in the Old Testament.
The scale of the punishments are the same between the Old testament and Kayle but the reasons for them being of that scale are different. The OT is much more metaphysical than Kayle's story. But either way, that's all I have to say about it for now. If I think a bit more on it and want to add anything, I'll come back and add it. Either way, thanks for reading :)