Some of those artifacts are real: like the pillar of iron which doesn't rust, and the Chinese aluminum buckles. I think it just has to do with the fact that Europeans were quite backwards in ancient times, so anything which was discovered in other areas of the world way before Europeans independently developed the same technology, seems like magic, or a fake.
Indians were quite adept at making steel from a very early time, hence the "iron pillar which doesn't rust". As for the Chinese, they seem to have developed and then somehow lost a technique to process aluminum ore.
As for the atomic war stories: give me a break! Ancient people were probably much smarter than most of us tend to give them credit for, but from there to presume that they had atomic weapons... let's just say you'd have to be pretty gullible to believe that.