Answer in message box, please!

#4: The modern day life jacket, in its current, Life Guard approved iteration, has saved countless lives. However, the knowledge used to create the current version came at the cost of thousands more. Why? Who did what research to eventually arrive at what we see today?

Much of the knowledge used in the creation of modern life jackets comes from experiments carried out by nazis on Jewish prisoners during WWII. The nazis would submerge prisoners in tubs of freezing water until they died, noting which positions resulted in the longest survival time. It was found that if the brain stem was kept above water, the victim could survive for leaps and bounds longer than the other subjects. This knowledge was first used in nazi flight jackets for when pilots bailed into the water, and then in nazi life jackets. Postwar, the knowledge was disseminated to the rest of the world and put to a more noble use.

At least to the why part: the earlier iterations made it easy for an unconscious person to flip over face down in the water, and thus drowning the victim.