TBH all the time I saw this phrase was about strong people in the broadest possible way. And always as a positive.
It’s very strange to see people defining strong in very narrow bigot way and then trying to spin the whole phrase into a negative. This thread is probably the first time I saw people take such turn.
It’s also very strange that people try to portray being weak as a positive. Sure, strong may have very different definitions from different people. Even borderline opposite. But turning the whole word into a negative… that reminds me of 1984. Weaknesses is strength, strength is weakness.
Whereas I always take this phrase to be refering to a military kind of strength. For example, this whole article tells us that Oda Ujiharu got the nickname "weakest" because of his military incompetence. Your own examples of strength in this thread tend to be mainly martial too.
This kind of strength - the ability to force your will upon others (which is what military strength is, and also the kind of strength that 'Strong Men' dictators have), motivates the (usually incorrect) comparisons to historical empires. There are other kinds of strength - moral strength, resilience, determination, vision, etc they're just not what I think is being talked about with this phrase.
I don't know where you get 'weakness' is being described as a positive in this thread. Weakness can also mean many things, but in this context, it means being susceptible to others forcing their will onto you. It's not a good thing, but differences in strength are natural and impossible to avoid. What is a good thing is when the great mass of comparatively 'weak' people realise that together they are stronger than the tyrant.
Rather than 1984, for an appropriate comparison I'd go to the Bible: - "God chose the weak things of the world to shame the strong."
A lot of „martial“ skills are needed in daily life. Discipline, planning, ability to operate both on your own and in a team both as a leader and a member. Even physical strength does help, even in modern world. A good CEO and good military commander skillset is very very similar. Just like good specialist and good soldier.
Whenever I meet this phrase, it's talking about specifically those „other kinds of strength“.
I'd even argue that there's no „strength“ in dumbly forcing your will upon others. It's a strength to lead people, to inspire them and get them to follow you. Charisma and leadership is a hell of a strength. But to physically force people... All you need is a number of, possibly weak, people and you'll likely succeed in bending even physically much stronger people.
And weak people banding together can build a tyrant regime. Soviet union is probably good example. Both at initial stage when workers kick started it. And in later stages when usually the weak life scum went to work for the security apparatus of said regime. And reading about other regimes, it seems to be a recurring theme that security apparatus is built out of weak miserable people who look for an revenge opportunity.