Edge cracks usually happen when the case is a hard clear plastic or a very thin hybrid. that model work adds heat and cold swings and UV exposure and grit, sweat, sunscreen, and bug spray. Those all speed up stress cracking. Corners near the buttons and charging cutouts act as stress points and every drop or flex concentrates force there. Taking the case on and off can finish it off.
Switch to something with a more rubbery feel that stays flexible in heat and cold. Opaque or matte materials tend to resist UV better than crystal clear. A thicker design with a soft inner layer and reinforced corners spreads out impact so the edge does not split. Skip ultra thin styles even if they look clean. Rinse dust out of the edges, keep chemicals off your hands before handling the phone, avoid leaving it on a hot dashboard or in freezing air, and try not to pry at the corners during removal. Thin and crystal clear. Prone to this.
