Park Chung Hee took a country that could not be a functional democracy, provided leadership and put it onto the path of economic success. Iirc, the reduction in poverty through that period is the fastest in human history (when you consider that China, that is an incredible statement).
I think people (still) assume both that democracy is superior economically for every situation and that people who don't have any food care about being unable to vote...neither of these things is obviously true. Indeed, in the latter case, we now have a good test case of poor countries adopting democracy early and they have generally not been successful as power rotates between various quasi-dictators who give massive handouts to the poor to retain power (without doing anything actually useful).
1945 to ~1947 were very rough in Germany even in the allied occupation zones (and that was at least partially an outcome of a conscious decision by the allies to not allow German industry to recover)
Grenada is something of a joke in this context - the entire thing came about because the communist government fell apart and started fighting internally, so it's pretty likely the regime would have shortly collapsed with or without the invasion