Nearly all countries grew quickly in the 1950s and 1960s for pretty much the same reasons. That applies to the United States, Britain, Germany, Japan, most of the rest of Europe, major parts of Asia, certain (but not all) parts of Africa.
World War II ravaged the industrial and production base of most of its participants (except those in North and South America), while killing a large number of people. At the same time, the "hot house" atmosphere of the war spurred a lot of technological innovation.
So you had a large base of intellectual capital numerator applied to an artificially low base of physical capital (denominator). The combination of a large numerator and a small denominator made for a high growth rate.
It was a great tragedy for those who were killed. But the survivors (and their Baby Boom children) did very well after the war.