Thank you for mentioning the effectiveness of the figure-four choke-hold / strangle-hold.
I wondered about how an older guy was able to take out a younger guy, but since you told me that it makes sense now.
I know some of the "older guys" are WW2, Korean war, or Vietnam vets and have killed an enemy in close combat before and could do it again if they had to.
Here is a link to a Youtube video of a pretty cool demonstration of the technique used to put an opponent to sleep performed here by Cris Cyborg...
I noted that the guy in the image you proved was not doing the hold properly. He did not have an effective left arm lock.