Actually, the answer you´re looking for would be ¨They did not realize they were being watched¨ If you read very carefully, you´ll notice that the lines from the passage never mention anything about the humans knowing they were being watched and did not mind. Also, the very first line if the entire thing says, ¨No one would have believed in the last years if the nineteenth century that this world was being watched keenly...¨ Which would imply that they were not aware that they were being watched during that time.
This line implies that humans, have been created in a sort of synthetic environment. Humans in this case, are now the most intellegent beings on the known universe, they have been monitored, similar to test subjects. These people/ this race, is more intelligent than man, and humans have been in an experiment this whole time.
