The perception of Japanese optics began to change in the 1950's...
https://imaging.nikon.com/history/story/0036/index.htm
...that led to the adoption of the Nikon S 135 rangefinder body, in lieu of Leica or Contax. The quality of the Nikon RF bodies led to the adoption of the Nikon F SLR.
"In 1950, The New York Times commented that Nikon cameras and NIKKOR lenses used by photographers for Life magazine were superior to those made in Germany, significantly enhancing the reputations of both Nikon and NIKKOR far and wide."
"It was in 1950 when Mr. Jun Miki, also a photographer connected with LIFE magazine, was taking a snapshot of Mr. Duncan with the Nikkor 8.5cm he had borrowed from a friend, a photographer who happened to be visiting him. At that time, Mr. Duncan did not take any special interest in the lens, simply saying "Oh, Japanese Sonnar?" However, later his attitude changed quickly when he was shown the enlarged shot, and he started examining the photo with a magnifying glass. "It's great! Very sharp! Take me to the company at once!"
"Then, Mr. Duncan, Mr. Bristol, another FORTUNE magazine photographer, and Jun Miki visited the Ohi Plant of Nippon Kogaku K.K. (the current Nikon Corporation). At that time, Masao Nagaoka, then President of the company, led the three to the lens inspection room and showed them a comparison of performance between the camera lenses carried at that time by Mr. Duncan and Mr. Bristol and the NIKKOR lenses, through a projection inspection instrument. They saw the distinct performance of NIKKOR lenses with their own eyes and purchased NIKKOR lenses for Leica on the spot. Then, carrying the lenses with him, Mr. Duncan went to the battlefront of the Korean War, and subsequently his magnificent photographs taken with the NIKKOR lenses were published in LIFE magazine. This made the NIKKOR lens brand known around the world."
It did not hurt that stories like this added to the legend of quality of the Nikon F
https://photodom.blog/this-tank-of-a-camera-actually-saved-a-mans-life/
"On this particular day, (Don McCullin) went out to document the severity of his environment with his trusty Nikon F in hand, not knowing that death was waiting for him around the bend. A Cambodian solider quietly sized him up, prepared his AK-47 and shot the man point blank. However, God had other plans, and McCullin’s camera stopped the bullet that would have been certain death for him. This solid camera ultimately saved his life"