The pirate put on the blindfold not because he could not see it, but to quickly adapt to the dark environment of the cabin.
When they got into the cabin from the deck, they took off the blindfold to cover the other eye, and used the previously covered eyes to observe the room. In this way, the eyes can quickly adapt to the dim light in the cabin and quickly see things around.
Someone has done verification. The subjects who had adapted to the bright environment were allowed to enter a dark room to complete a task, but it took the person 5 minutes to get it done. However, if the subject’s eye is put on an eye mask for 30 minutes before entering, the time to complete the same task will be greatly shortened.
Some Western reports also say that this tactic of adapting to light / dark environments is also used by the US military today. A US version of the book “Night Warrior Handbook”, which is produced by the Marine Corps, has a similar saying: When the naked eye attacks the enemy at night, try to use a burst shot and close one eye to avoid being blinded by the flame of the muzzle.