It was an idea that struck "at once" after a lot of other very intellectual pursuits, all of which had to happen for the epiphany to have occurred. I seem to remember reading that General Relativity struck Einstein similarly, but it probably helped that he had thought about the subject beforehand.
No, and I'm glad you FINALLY mentioned this. This is the distinction I tried to make with JCamilo back when we started. Here's precisely what I said: "I did state that "intellectual" needs to be distinguished from just 'everyday learning" (I'd add thinking) and "academic" and that I think it resides somewhere in the middle. Again, most "everyday learners(/thinkers)" do not come up with something like "Negative Capability," which is the product of much reading and reflection. But because it was done outside of the academy, it couldn't be said to be "academic" either, so "intellectual," to me, seems the right way to describe it."
So, no, I do not think everyone that "thinks and ponders" is an intellectual. Rather, I tried to argue that my usage was for those that think and ponder a great deal on certain abstract subjects, aesthetic theories being one of them. Keats did this. He clearly thought more--longer, deeper, broader--on the subject of poetry than do most, and it lead him to come up with several theories that still resonate today. To me, that's THE mark of an intellectual: think a lot on a subject, come up with concepts that continue to resonate... or at least show some thoughtful engagement with the various intellectual theories and ideas at the time.