I can see a screen protector (glass maybe).
if it’s glass can be the responsible of the crack, because it rises above the frame, the original glass is built inside the frame. You can see the crack is just up front the edge of the screen protector, so it could be a precise and well concentrated hit from the screen protector edge.
Mind that the ceramic glass is scratch proof, not drop proof; they are very different physical processes (I’m a mechanical engineer) and often they are in opposition (an hard material can be really though to be scratched, but looses the elastic properties good for drops).
My personal suggestion is to avoid glass screen protector (screen protectors at all) because they concentrate the energy of impacts on the edges making impossible to avoid damages from drop. So you are over protecting from scratches (that are very well managed by Ceramic Shield) and at same time over weakening the drop resistance, making the original design of the glass inside the metal completely useless.
I personally use the bare phone with a magsafe wallet that protects the back. I have a cover just in case of hard times (beach, mountain, etc.). I also have apple care for iPhone, that can cost less than a lot of cases that ruin the phone experience and that cannot guarantee the absence of damages; consider that iPhones are commercially stable in the second hand market, so the Apple care is also a way to rise the value of the phone to the top before reselling it.
