Why do some economists believe manufacturing jobs began to move from develpoed nations to emerging nations?

As the more developed nations have a better access to capital and education, they gain a comparative advantage in using their limited labor force for other (more profitable) means. The less developed countries on the other hand have an abundant access to a cheap labor force and have a comparative advantage in this area. Since manufacturing requires little job training (none if it is automated actually) the emerging nations are more prone to focusing their resources in this sector.