As others have noted, the solo founder list is filled full of people that had immense help from other people, typically from day one.
For example: Henry Ford
He had half a dozen people building his first vehicle for him, most of them contributing their time to help at no cost, while he directed the implementation/vision/ideas. This is the first version of his quadricycle vehicle [1] he built in his little shed. Ford did some early experimentation work on his own, it wasn't very long however before he invited some extremely talented specialists to join in helping him, just to basically see if they could all pull it off. Ford had a high talent for gathering skilled specialists to follow him (messianic leader, he managed to do it throughout his career), all of which were better at specific tasks than he was (whether blue print drafters, or metal workers). Solo founder? Ford Motor wouldn't exist without Ford and it wouldn't have existed without the critical day-one contributions of those particularly talented people (some of which stayed with him for many years). When Ford built the Model T, he pulled together a very small team of hyper talented people just like with the quadricycle, and they did the actual work / implementation, while he played general (to take nothing away from that role, it's at least as critical as the other roles).
For example: Henry Ford
He had half a dozen people building his first vehicle for him, most of them contributing their time to help at no cost, while he directed the implementation/vision/ideas. This is the first version of his quadricycle vehicle [1] he built in his little shed. Ford did some early experimentation work on his own, it wasn't very long however before he invited some extremely talented specialists to join in helping him, just to basically see if they could all pull it off. Ford had a high talent for gathering skilled specialists to follow him (messianic leader, he managed to do it throughout his career), all of which were better at specific tasks than he was (whether blue print drafters, or metal workers). Solo founder? Ford Motor wouldn't exist without Ford and it wouldn't have existed without the critical day-one contributions of those particularly talented people (some of which stayed with him for many years). When Ford built the Model T, he pulled together a very small team of hyper talented people just like with the quadricycle, and they did the actual work / implementation, while he played general (to take nothing away from that role, it's at least as critical as the other roles).
Ford as a solo founder is a big stretch.
[1] https://en.wikipedia.org/wiki/Ford_Quadricycle