On the Twitter point, the idea of Twitter was to enable groups to text message each other. It was a very obvious idea because texting groups was awful on dumbphones and people wanted to do it. What Twitter became was something that wasn't really foreseen, but is a textbook exercise in pivoting as you see what your users are doing.

And as such, that's essentially how ideas solve problems. Very rarely does someone see a problem and come up with a perfect solution first time - an entrepreneur sees how their solution changes the problem space, and pivots with their users needs until the solution fits. And then you have this amazing product that apparently solves something that isn't a "problem" - because the product has changed to eliminate the original problem and enable the user to do something useful.