Rebirth 1,000 Years After the End of the World

1,000 Years after the apocalypse, science and technology and culture were disconnected, and new humans dug up the ruins of the 21st century and shocked the world. How could the ancients fly to heaven on an iron bird? Are these rectangular iron boxes coffins? Why did some ancient people grow gold teeth? What is the product of internet celebrity as mentioned by the ancients? Is what the ancients often called "bang banging the sky" the real reason for their destruction?