The real problem with scale close to whole countries is that if your money isn't contributing to the growth of the entire economy, you can't really get a return at all.
You can't extract value out of an economy that is stagnant, if the money you are pumping in is merely recirculating in zero-sum mode.
At the small scale this can work, because there are enough small-time losers who lost money when you got it without hurting the balance of the economy, but at the large scale this cannot since there aren't enough losers to lose money to pay you off (or alternatively, there is a war going and/or the government is buying).
So any investment portfolio big enough which doesn't move the economy to be more productive is bounded by the entire economy and in general do worse, because the market might be reacting to the fund & preying on it.
Also "more productive" is a very weird term - giving people public transportation, fast internet or cheap child-care can make a society more productive. Underemployment of intelligent people into subsistence levels of productivity is basically a crime perpetuated by well intentioned folks from the pre-automation era.