Here's an example of Acemoglu's thesis from The Times Magazine article:

Consider Acemoglu’s idea from the perspective of a poor farmer. In parts of modern sub-Saharan Africa, as was true in medieval Europe or the antebellum South, the people who work the fields lack any incentive to improve their yield because any surplus is taken by the wealthy elite. This mind-set changes only when farmers are given strong property rights and discover that they can profit from extra production. In 1978, China began allowing farmers to benefit from any surplus they produced. The decision, most economists agree, helped spark the country’s astounding growth.

Acemoglu and his Why Nations Fail collaborator James Robinson aren't simply arguing that incentives matter—they're arguing that if countries do not give their poor any possibility for social mobility, whether “through property rights, a reliable judicial system, or access to markets”, their economic engines will be stuck in neutral. This realization means that the current foreign aid strategy of one-off programs or monetary gifts are essentially useless if given to a country that fails to invest in their poor and vulnerable. The real focus of aid should be on deep political and economic change.