I recall an old Scientific American story about cracks in glass. They pointed out that when water gets into a crack, it makes the crack grow. In theory any kind of little scratch on a glass surface can slowly grow over the years.
Tempered glass does fail “explosively.” The classic demonstration is called “Prince Rupert’s Drops.” In this demonstration, blobs of liquid glass are allowed to fall into water and cool. Most shatter, but some do not. Because the surface cooled and contracted first, extremely fierce forces build up inside the glass, and potential energy is stored as in a compressed spring. The long-tailed “droplet shape” of glass is extremely robust, and it can be struck hard with a hammer. This demonstrates that the hammer blow is nothing when compared to the huge forces inside the glass, and that’s why tempered glass is so strong. But if carborundum is rubbed on the surface (causing tiny scratches), the glass explodes into powder. Or if the long tail on the blob is snapped, again the whole blob of glass explodes. The first major crack releases some stored energy, which stresses the neighboring glass so much that it also cracks, etc., and a wave of destruction passes through the whole thing.
Also, if you shoot a bullet at the side or rear windows of a car, you don’t get a bullet hole. Instead the whole window turns into fragments. The same thing could happen if a tiny scratch finally grew big enough to affect the neighboring glass and release the stored energy.