I recall an article where Facebook or Uber or some other big tech co found something similar when they added some optimizations, and it turned out that it was being accessed by an entirely new market that couldn’t even load the page before.

I wonder if it’s a similar thing here. Maybe the lighter embed is small enough that a huge swath of people is actually able to load a video now, but they bounce because playback is too slow on their device/connection. It would shows as a higher percentage of “person stopped watching video” instead of (nothing, because they never fully loaded the player).