Complex life evolved on the Earth's surface, but not on Mars or other planets in the solar system because on those planets, early surface life was killed by UV radiation.
He was a formidable polymath, doing important work in mathematics, physics, logic, the study of formal and natural languages, and many other disciplines.
Teenagers often struggle with an overwhelming sense that nobody likes them, that they're not as good as other people, that they are failures, losers, ugly or unintelligent.
As it was free and dead simple to use, there was no barrier to adoption; but the viral spread was only possible because it was such a big problem and it was so much better than the alternatives.