The prototype is typically fast and easy to build. It’s a simple demonstration that a particular idea, technology, or solution is possible.
If the prototype demo goes well, the tricky part is translating it into a product that is ready for production (i.e., ships to end users).
All the complexities and edge cases that get glossed over in the prototype phase have to be hunted down and resolved. And they’re typically hard and take a lot of time.
Prototypes will get people excited and motivated, but sustained effort and energy over time is required to ship.
That’s the hard part.