I think you might be operating with a romanticized definition of what a genius is.
In fact a common definition of (higher) intelligence is the ability to see patterns (abstractions, properties, laws) in an otherwise random looking world.
Think of Darwin looking at birds, animals, vegetation, and being able to come up with something like the Laws of Natural Selection. Even today 99.999% of people would not see those patterns.
Think of Kepler looking at random movement of stars and planets on the sky and being able to come up with the Laws of Planetary Motion. Same thing, today 99.999% of people would not see those patterns.
On a much lower scale, the character in this text displayed a similar ability to see in otherwise random looking objects new properties, arrangements, and applications.
I think you are judging here based on the small scale of his achievement (rolling table, who cares, $50 at Home Depot could make better, right?) but you are failing to consider for the absolute-zero (or close to it) in resources that the guy had at his disposal.
For example an achievement like this:
https://www.economist.com/science-and-technology/2018/09/06/...
, in my opinion, has to be amplified in our eyes to compensate for the difference in resources availability in a typical bio-tech-lab in say US, and what was available here.