I tried to install the iOS 13.3 update manually, and it failed silently a few times, so I restarted the iPad and got it through the "preparing update" phase. Then I left it plugged in overnight again, and still no update. But when I woke it up this morning, it told me that it would install now. Since I wanted to use it, I tapped on "later", at which point it asked for my passcode and said it would install tonight between 2:00 and 4:00. What's automatic about this update?