I'm really struggling to match your definitions of weak and strong here to anything like normal usage.

I think you're saying that it's strong to be employed? I'm not really sure how that matches up to being against the things you mention in connection with "weak".

Incidentally, I don't know if you intended this, but building roads and sewers and policing are, in most countries, socially funded programs.

It's a metaphor, "strong" and "weak" refers to the ability to overcome the "hard times", whatever that may be.

Basically if you experienced the direct consequences of a "hard time" (a demagogue, a famine, a recession or financial crisis, SCRUM, or whatever) you will be more aware and resilient to allowing the things that caused that to happen than if you never experienced it. That's "strength".

It is of course true, we see it everywhere in nature, but it's perhaps often more due to hard times eliminating weakness than actually creating strength.

Good times tend to increase the number of people who don't know how serious bad times can get, don't realize the importance of principles that were obvious to the people who survived the bad times.

So "strong people" can perhaps be "created" equally in good times as well, but they are increasingly outnumbered. During hard times the "weak" are eliminated.

This being Ycombinator one can consider the example of how any crazy idea gets funding during good times but during hard times the ideas that actually have legs remain. ;-)