It's a morality play, like the Pied Piper of Hamelin. The numbers also vary depending on the translation and source material, as low as 70 in some versions.
It's also funny that the actual event, the alleged looking into the Ark, is not documented anywhere in the story. There is no mention of who looked, how many people looked, why they looked (were they just checking to see if the Tablets which were actually the important part were still there?) or any other details. There is also the classic "proof" by something totally unrelated.
The large rock, on which they set the ark of the LORD, is a witness to this day in the field of Joshua of Beth Shemesh.
"Thet thar rock, out in the field. Yup, thet's the one."
How can a rock in a field be testimony of anything?
This tale has all of the hallmarks of a fireside tale, embelished and expanded, designed to explain cultural mythos and the idea that the average joe should not mess around with the realm of the priesthood.
There's a good chance that there is a kernel of truth underlying the story. If the Ark really was returned, it's possible that during the interaction between the peoples, those of the village may well have caught something from the Philistine visitors. Such an event could have lead to a large death toll, particularly in relation to the village size.
Coming shortly after the only significant thing to have ever happened, it is not surprising that the folk saw a connection between the arrival of the Ark and the sickness. Since there was a prohibition against looking into the Ark, the reasonable assumption for those who survived was that some person or persons unknown must have looked into the Ark.
Aslan is not a Tame Lion