1. He was not looking backward carefully in turning left.
He looked behind with a rear-view mirror, not but a side mirror. So, he did not realize the bike in the blind area.
In fact, checked the blind area of the rear-view mirror in the car. The area was 5m behind the car and 50cm from the right side of the car.
2. The person concerned was not looking ahead carefully.
The bike, which was in the blind area of the rear-view mirror of the car, was so close to the car.