Rather than a singular "question" that seems stupid, consider prime numbers. People toyed with prime numbers for centuries, asking all sorts of questions, with little-to-no impact on the vast majority of humans. Fast forward to the age of telecommunications: suddenly massive innovations in cryptography are being built on knowledge of prime numbers that previously was a novelty.
Yeah, math has a lot of ideas that seemed like silly puzzles when first explored. The term "imaginary numbers" was originally an insult (from Descartes!) for math involving the square root of negative numbers.