Why a person with pneumothorax has the right lung was collapsed why left still inflated?

It's not necessarily the case that a person with pneumothorax would have only their right lung collapsed while the left remains inflated. Pneumothorax can occur in either the right or left lung, or even both lungs in some cases.

When pneumothorax does occur, air from outside the lung accumulates in the pleural space, which is the cavity between the lung and the chest wall. This accumulation of air causes the affected lung to collapse or partially collapse as the lung tissue loses its normal lung function due to pressure imbalance

The specific lung affected by pneumothorax can depend on various factors, including the cause of the pneumothorax, the severity of the condition, and individual anatomical variations. It's not entirely accurate to assume that the right lung tends to be affected more often rather than the left during pneumothorax