I figured you’d bring them up.
Disney started in a garage too, and that may be a better example of “from scratch” since AFAIK there was very little in the way of outside help and their/his product was fairly defined from the get go.
HP not so much, they started as tinkerers. Apple, rags to riches to rags, they were in full death rattle when jobs came back with Apple clones kicking their ass. Gates, defined -some say stolen-product, but regardless building on that concept/product.
Still these examples are all comparing apples to bowling balls. I don’t think a Zuckerburg’s business experience would qualify him a CIC. Real estate development is a very different animal, especially at Trumps level.
Buffetts, Gates’, and others beginning posts are way more modest, and their endpoints way past trump’s, and their holdings far more complex than trump’s, as well. Yet, I wouldn’t vote for any.