Why were the French infantry columns vulnerable during the attack on Wellington’s centre?

During the attack on the allied centre at the Battle of Waterloo, the French infantry columns were highly vulnerable for two primary reasons:

• Formation: Many of the attackers were organized into unusual, deep divisional columns—approximately 200 men wide and 24–27 ranks deep. This dense configuration prevented the soldiers from returning fire effectively against the British lines.1
• Artillery Exposure: Because of their deep, narrow formation, the columns were exceptionally susceptible to artillery fire. When they advanced without cavalry support, they were met with the maximum firepower of the British infantry, leading to severe casualties.1