That said, I feel like the people praising "the quiet life" are missing that this man found a companion at ~20yrs old and with that companion had a family and kids and grand kids.
Plenty of people never find that anchor/base/partner
https://www.pewresearch.org/social-trends/2021/10/05/rising-...
It's arguably easy to be content when you have good support around you. Bad or no support and it's much harder.
He didn’t seek fame but I wouldn’t describe this man as a quiet one, he probably lived in a rich social network full of visitors, work colleagues, veterans, friends etc. There are very few people aside from egotists who seek large scale recognition for their work etc.
No doubt a good partner multiplies contentment, but they shouldn’t be facing a void of it either. Lastly, if you find that your contentment is being pulled and pushed and stomped on by external factors, then do what is needed to gain control of it again - anyone can achieve this, and if someone in a land of possibility thinks they’re the exception, that the world really is getting in their way, they’re holding themselves back with that very thought.
The takeaway being what you mentioned. Having a long term loving caring relationship is the biggest indicator.