Or consider the history of the Fast Fourier Transform (FFT) , one of the most useful algorithms known to man. John Tukey had an idea for speeding up the calculation of the discrete Fourier transform: Dick Garwin saw that it was incredibly useful and pushed it, while Cooley wrote the program. But the idea goes back a bit further in time: Good published a related idea in 1958, L. H. Thomas in 1948, Danielson and Lanczos in 1942, Stumpff in 1939, J.D. Everett in 1860, A. Smith in 1846, and F. Carlini in 1828.  The first treatment of the algorithm, and the only one as general as the Cooley-Tukey article, was by some geek named Carl Friedrich Gauss, back in 1805 (17 years before Fourier published his work) . An unpublished paper on this topic was included in Gauss’s complete works, published ( in Latin, of course) in 1866. If someone (a Jesuit?) had just looked in the right place and talked to Babbage, the British would have been doing digital signal processing in the Crimean War.
–gcochran9, “Battle for the Planet of the Low-Hanging Fruit” @West Hunter
Emphasis mine. I have always been fascinated by instances where small changes in history would have had great effects down the road. This was one. There are many, many more.