From the article: “Jordan Neely, 30, was shouting and pacing aboard an F train in Manhattan on Monday afternoon . . .” This tells me that Neely was under the influence of drugs and acting erratically. If it was fentanyl, it would have affected his respiratory system, much as it did George Floyd. Fentanyl makes one very vulnerable to restrictions of the blood flow to the brain. How would the Marine know Neely was extremely vulnerable to his restraining maneuver?
“How would the Marine know”
He likely would not have known this specifically.
But most people who learn the chokehold or “sleeper” hold learn at the same time why it’s dangerous and that you’ve got to release it ASAP to avoid this result.