Stepping back it’s fairly obvious the opposite is true. They got so good at that thing by focusing on it. Focusing on something, by definition, means not paying attention to other things. You see where this goes…
You can't be really good at something by focusing only on it.
To be good at software design, you need to be good at understanding computers and people. You need to understanding programming, design, marketing, hiring, management, etc.
Scott Adams developed this into a concept he named "The Talent Stack".
You can easily verify it: find billionairs who got rich from X, study their profile, you will find they have a wide range of skills outside of X.
For any such X you can also find many individuals with exceptional ability/knowledge about X but not much else, and they are often far less successful from people with a wide range of skills.
He's a lawyer and economist, a National Master chess player, and a (multiple) startup founder (PayPal, Palintir, etc), investor (first outside investor in Facebook). And he is actually also a "hedge fund guy", but he does not seem to be a software guy of any sort.
As far as I can tell from a very great distance, he is highly intelligent and has been demonstrably successful across multiple domains of expertise, and certainly smarter than your previous remark would seem to imply.
https://en.wikipedia.org/wiki/Peter_Thiel
EDIT: just saw your kind response. Perhaps just read through the above wikipedia page. He's obviously a very polarizing individual, but whether you personally like or hate his politics, it seems pretty clear that he's a pretty brilliant person -- as smart as Reid Hoffman on the other side of the aisle (whom he is good friends with.) It seems wise to be friends with (and have friendly debates with) people who disagree with you, especially if they are very smart. Iron sharpens iron. Thanks for elevating the level of discourse!