I do see the problem with the apparent date of origin and the difficulty of creating maize -- what we now tend to call "corn" as if it were the only thing that had that name -- from teosinte. The prevailing opinion in official circles is that humans were still hunter-gatherers in the 8th millenium BCE. Here's the thing, though: we are always forced to rely on only the evidence that has survived from that time, and also has been found by people able to recognize it for what it is. Stone tools from many thousands of years ago are well known to modern science, but hardly anything like leather or fibers that might have been used to bind any of those stone edges to any wooden handles have survived. We can only speculate from the shape of the surviving stone that it might have had a handle. The evidence considered to show the development of agriculture is what, exactly? Recognizable tools used for working the soil? Or the tools used to process the grain ("mill stones")? Or just scattered remnants of food in former dwellings and camps?
This is an important question because I think there are some overly broad assumptions hiding other possibilities than the cultivation of grains being the real beginning of deliberate agriculture. The main problem, as you seem to be framing it, is why this difficult to develop crop was developed so early when there was no apparent reason for them to make so much effort. There should have been no basis for the ancient people who did so to think there was a reason to put in the effort. What if there was a good reason? What if they were growing something other than grain already, and it was a reasonably good source of food? Then they would have the basic idea of agriculture already and could have lived on their other crop(s) and just cultivated teosinte as an additional/supplemental food source for thousands of years, gradually improving it.
Would there be obvious remains of some soft root crop in those former dwellings and camp sites? Maybe the remnants of grain were just more durable than other foods. And even if the root crop was detectable, how would archaeologists tell that some root crop was cultivated instead of just gathered? Isn't the consumption of grain recognized by the stone tools used to process it? ("mill stones" of some sort.) If a root crop didn't need stone tools to eat, but could just be eaten raw, or maybe roasted by jamming a stick through it and roasting it over the fire, how much evidence of the consumption would be left thousands of years later? Instead, what would survive would be the hard shards of grains, and the stone implements used to break them down.
As for who actually developed it, the date is suggestive of some population displaced by the changes in sea level at the end of the ice age. They may have had crops in their former habitat, and been unable to get all of them to grow in their new habitat due to changes in the climate that accompanied the end of the ice age. That might explain their efforts to develop an apparently unpromising crop like teosinte. They had the basic idea of agriculture from their previous lifestyle, but could no longer grow all of their old crops. Desperate, they worked with what was available. But still, I know of no reason to think they weren't the ancestors of the historically known peoples who lived there.
Like ancient Rome, we today are once more importing every form of exotic superstition in the hope of finding the right remedy for our sickness.
-- C. G. Jung
Richard Wilhelm: In Memoriam (1930), CW 15: pg. 60