Gianni Agnelli was once asked the same question by (a young) Jeremy Clarkson (check the quick vid below).
L’Avvocato replied that Italians in 20th century developed a multitude of small mechanical repairs shops to assist consumers fixing their cars (the car market was booming in Italy and this created a wealth of opportunities for ingenious people to put themselves to work).
These small repair shops usually employed all kind of people, especially poor guys with no money but with a lot of passion for fast cars, huge imagination and gusto.
After they gained some experience, these guys used their creative approach not just to repair someone’s else cars but to manufacture their own.
At the times there were no over-zealous regulations so this could be done even by a small family shop.
Many of them did not last more than a few years, but occasionally a few thrived and developed into great brands that have made the history of cars.