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WieWaldi Sure, I can name Richard van Basshuysen. Today, he is referred as the father of the direct injection engine for diesels.
I looked up van Basshuysen. Here is what I found. (I know you read German).
https://de.wikipedia.org/wiki/Richard_van_Basshuysen
Kfz Schlosser (automotive mechanic-plus), then training as a mechanical engineer in the German system, then practical work in the research department in engine and transmission development. He was not a beginner inventing something in an unfamiliar field. That background gives an enormous and varied amount of experience in the field, combined with theoretical knowledge.
James Watt, by what you described, also had practical experience; his learning path was unconventional from what I read just now.
Both men would have had years of practical experience preceding their inventions.
I don't want to link this to any of the discussions about music here.
WieWaldi James Watt is another example. He did not invent the stea