AFAIK the real predecessor to USB was Serial cables and those were an absolute shit show. USB set out to create a more usable interface with a lower profile and cheaper cost. In many ways the minor flaws in USB becoming common gripes is USB becoming a victim of its own success. I don't think they originally set out to become a power charging standard so the frequency at which devices were plugged in increased over time .

I don't even know that I would call it inexperience. I just think a major part of the first pass was selling the idea of USB. You can design a perfect cable, plug, and protocol, it doesn't mean anyone will use it. Most investors don't know much about the technical details of a product. They do, however, understand the price. If you're trying to make a difference in the world, you don't always get to do it with style and quality.