Do not know about them specifically, but my guess is some just took over ancient ruins and created a story to explain their creation. It would be impossible to tell the difference now, assuming of course our dating methods are messed up when the nukes, or asteroid hits, occur. You should not assume you were the first advanced civilization. And we do. Which creates an observational bias.
Indeed.
I would enjoy a conversation with you, at some point in time.
Thanks for your logic.