Green fluorescent protein (GFP). A curiosity-driven marine biology project (how do jellyfish produce light?), that was later adapted into an important and widely used tool in cell biology. You splice the GFP gene onto another gene, and you’ve effectively got a fluorescent tag so you can see where the protein product is in the cell.
Jellyfish luminescence wasn’t exactly a hot field, I don’t know of any near-independent discoveries of GFP. However, when people were looking for protein markers visible under a microscope, multiple labs tried GFP simultaneously, so it was determined by that point. If GFP hadn’t been discovered, would they have done marine biology as a subtask, or just used their next best option?
Fun fact: The guy who discovered GFP was living near Nagasaki when it was bombed. So we can consider the hypothetical where he was visiting the city that day.
“Norman Borlaug’s Green Revolution” seems to give the credit for turning India into a grain exporter solely to hybrid wheat, when rice is just as important to India as wheat.
It seems that the high-yield rice used in India’s Green Revolution derives from the Chinese crop breeding program.
Yuan Longping, the “father of hybrid rice”, is a household name in China, but in English-language sources I only seem to hear about Norman Borlaug, who people call “the father of the Green Revolution” rather than “the father of hybrid wheat”, which seems more appropriate. It seems that the way people tell the story of the Green Revolution has as much to do with national pride as the facts.
I don’t think this affects your point too much, although it may affect your estimate of how much change to the world you can expect from one person’s individual choices. It’s not just that if Norman Borlaug had died in a car accident hybrid wheat may still have been developed, but also that if nobody developed hybrid wheat, there would still have been a Green Revolution in India’s rice farming.