Why did my MacBook Air screen crack unexpectedly?

I bought my macbook air 4 months ago i only used this thing like 3 times, a few days ago i opened it to order flights then closed it normally when i opened it back up the bect day it had a small screen cracked bottom left and screen lines, apple told me i must of shut it on something. Apple this is a scam and too many people are dealing with the same situation. Im not even a tech guy so I barley use laptops. This is a DEFECT. I am not paying 500$ for a new screen. I honestly will never buy a apple product again if they dont fix this situation.

[Re-Titled by Moderator]