Well nobody knows because no historians wrote down the process when it was invented. That said, it was probably just invented on accident. Some cheese people were storing in a cave got accidentally inoculated and someone tried it and went "huh, this didn't make me sick and tastes pretty good. I'll add some to the rest of the cheese I'm storing too!".

By accident, followed by a dare, I assume. This was probably how many cheeses, yogurts, beer, etc. were invented. It didn't kill the first people who ate it, and they found it tasty, so they kept recreating it until they found ideal conditions.

As above, basically an accident with stored cheese, but you couldn't afford to throw it away in the middle ages. The same goes for many historical recipes where the initial object was to use up food that had imperfections.

as other have said, probably accidentally at 1st. old cheese, you could toss milk in to a sheep stomach to transport/hold it. the enzymes caused it to curdle and the motion help mix it up and solidify it.

I feel like 99% of food came about by something random happening and then someone daring someone else to try it.

"Ewww, the cheese got all moldy! I give you 3 drachma to try it"

And of course, for all the stories about 'why did people try to eat XXX?', there are famines, and when there are famines, humans, like all animals, will attempt to eat anything that can fit in their mouth.

Like surstromming. How hungry, and how determined do you have to be to eat that shark that as a society you figure out the many steps needed to render it edible?

It's just fermented herring, you take the fish, add salt and leave it be.

I think that's harkarl. Sustromming is herring I believe

Had some this summer. Not bad with pickles and onions

I was a cheesemonger for 10 years. Cheese is older than writing so on some level it's guesswork to figure out how some things came about. The first blues were almost certainly accidents.

Cheese, in general, is a great environment for mold to grow, so to get bluing, you need the mold spores (and mold spores are EVERYWHERE, especially in cool damp places like caves and cellars) and air pockets. Most traditional cheeses don't have intentional air pockets but cracks will form over time here and there from weight, handling ect. It wouldn't take a lot from there to go "hey, I like the moldy parts" to "how do I make more moldy parts" and doing things like finding which cellars made the moldiest cracks, dropping from a height to make more fissures, and mixing in moldy stuff to try and get more. (Roquefort was originally made by molding loaves of bread in the caves and grinding them up into the curd) over time real recipes get developed and cheese gets made with with the intention of blueing it.