Cracked iPad Air screen, no idea how it happened

My iPad’s screen now has 2 long cracks in it, one goes from one side to the other, the other starts near the edge of the first crack and goes across the screen. The problem is that they both occurred when I wasn’t using it, and don’t think I left them anywhere unusual. They both happened when it wasn’t charging, and during a time period when I left it alone for a while, but other than that there aren’t any similarities that I can think of. Is there a concrete answer as to why they happened? Is this a common issue?