No, he didn't make it up out of thin air.
If you read Russell closely, you will see that he actually sent Nagell documents of what he thought the story was.
It was the same with William Martin, the assistant DA of Garrison, who visited Nagell in prison. Nagell early on asked
him for their theory. Once he heard their theory then he could tell them his 'story.'
Have you not noticed that there is not ONE IOTA of evidence to back up ANYTHING Nagell said?
It's quite comical. A complete 100% absence of any corroborating evidence!
But conspiracy theorists eat it all up.
fred