The conclusion can be that the creator was angry and malevolent when he made the tiger, but it comes as a wonder that the same creator made both him and the lamb. It is so absurd that the narrator himself asks the question whether it's possible that there are more creators than one.
Satire is used by him to show that being a carbon copy isn't the best way to live, and that there is a better way. His real target is society. He implies that everyone tries to build character, but they continue to do the same thing as everyone else.
