There may have been a small crack out of view, like under a cowl at the bottom of the window. When it reached a critical length, there was a catastrophic failure. Temperature cycling alone won’t make a window fail. There has to be a crack somewhere, and temperature cycling slowly enlarges the crack. I had this happen with a safety glass shower door. I was in another part of the house when I heard it explode. There were little pebbles of glass everywhere.