Don’t worry, you’re not the only one. There are plenty of strong people, including famous strongmen like Jouko Ahola ( he said it himself in his documentary), who have a weak bench press.
The reason you have a weak bench press is because the chest muscles (the most important muscles for the bench press) are not used as much in everyday life and in most strongman and powerlifting training exercises such as the deadlift and the squat, as much as other muscles such as the arm, leg & back muscles. So unless you frequently perform the bench press or do push-ups it’s only natural for you to have a weak bench press. Of course, there are people who are endowed with stronger chest muscles and are naturally better at bench pressing but even if you were to analyze such people you would be hard pressed to find someone who can lift more than 100kgs/220lbs without any previous chest training.