I've come up with a lot of ideas that I just didn't have the ability to make happen, just to see it happen ten years later and someone else get rich. One in particular, a small, simple idea, the 550 cord quick cutter. Attaches to gear so you can rip a tie down without fucking with a tool. Now they make 'em but it took 'em three generations to get it like mine. I got the idea in turn from a coupon cutter my mother had.
But when I was studying math, you learn about calculus and how it was discovered by two different people in two different countries at the same time. Neither met each other and Newton invented it for physics while Leibniz invented it for pure math or philosophy. They accused each other of theft until the day they died, never having met each other, one in England, the other in Germany. I might add it was done during a plague and in secret by Newton, so, no chance of theft or collusion.
Fast forward and we have Moore's Law and other understandings of how the natural world works. Turns out we all have a similar base knowledge that we all share and from that similar ideas will pop up (all publicly schooled people for example). Our population is growing so the chances increase of overlap of ideas.