Why did it take ten years for Odysseus to make it home?

It took Odysseus 20 years to make it home. 10 years at Troy and then another 10 years trying to get home. The reasons he doesn't make it home is because he has made Poseidon (god of the sea) mad. Also he runs into goddesses that keep him on their island to "take them to bed", and his ship mates open the bag of winds that takes them off course.