Answer:
because he did not stumble upon the invention just out of sheer luck.
Step-by-step explanation:
In the lesson "Luck Favors the Prepared", Charles Goodyear's invention of vulcanized rubber is an example of both preparation and luck because he did not stumble upon the invention just out of sheer luck.
Goodyear had been experimenting endlessly with natural rubber in hopes to find a way to make the rubber more durable, elastic, or stretchy. He attempted many times and failed miserably before he accidently invented the vulcanized rubber. Had he not been preparing for it continuously, he wouldn't have stumbled on his luck.