One ties oneself in knots if one promotes "democracy" above all. What's valuable is freedom. Democracy is just one means of encouraging that, and it doesn't always work.
>But they didn't and they couldn't.
They most certainly could have.
I don't think so. With their half-life they'll never be able to overrun much of the world. And thing is, we'll never know now. It's your opinion vs my opinion.