Usually two reasons. Bad focusing by the camera or camera shake.
Try a long range photo with the camera propped up on something and use a delay timer. That will eliminate camera shake. If it's still blurry then it's the camera focus or digital zoom that are poor
At 10x or higher zoom, even small hand movements can lead to blur, especially if lighting isn't ideal. Samsung’s image processing at that range tends to apply strong noise reduction, which can smear fine details.
Also worth noting: if the phone is warm from use or sunlight, autofocus performance can drop and the camera may miss focus, particularly at long range. Try tapping to focus manually and using a delay timer with the phone stabilized for best results.
