the.com/turn a blind eye

means To deliberately ignore something you know is happening, pretending not to notice because acknowledging it would force you to act.

from Popularly traced to Admiral Horatio Nelson at the Battle of Copenhagen in 1801, who was blind in one eye and, when signaled to withdraw, supposedly raised his telescope to that blind eye and said he simply couldn't see the order. True or not — and historians debate how much is embellishment — the phrase stuck because it so perfectly captures willful, convenient blindness: not an inability to see, but a refusal to.