Why is it significant that all four young lovers fall asleep again at the end of Act lll ?

I'm assuming this is referring to Shakespeare's: A Midsummer Night's Dream...

Explanation:

The significance in all four lovers falling back asleep because it marks the end of the love spell. When all four lovers fall back asleep, their love spell can be removed and they can return to loving the one they love again. This scene foreshadows that the end of the play will come soon, as the main climax of the story is resolved. Hope this helps :)

the simple predicate of the sentence is camped.