I read a book called The Lost City Z which tells of explorers from the 19th century who found evidence of roads and water systems, etc. Some satellite images have confirmed this from what I understand. The problem is the jungle very quickly reclaims structures and other evidence.
Yes, the Amazon is full of ruins. It’s estimated that most of the jungle used to be farmland. It was only after their civilization collapsed that the rainforest took over. So I guess the answer is that man didn’t make the rainforest. It’s kind of a dumb question.