Understanding atoms.

[Darwinian]

I suggest that it was pure chance, or luck, depending upon your point of view.

Imagine if they hadn't come together in quite the way that they did. Then the universe would be unstable and incapable of supporting life and you wouldn't be here to ask the question.

Or, you would be asking the same question of a slightly different universe. I can imagine that there are an infinite number of universes out there in hyperspace and only by chance do some of them create stable enough environments for life to evolve and ask these questions.