Let's solve this mystery

So what actually was the cause behind the Akkadian collapse?

We know from previous papers that there’s substantial debate over the primary cause of the Akkadian Empire collapse. Socio-political failures and climate change rank pretty highly in discussions. 

Weiss et al. (1993) argues that it was a combination of political failings and drought conditions caused by multi-centennial climatic phasing. Through analysing sediment stratigraphy from sites near to the old Akkadian settlements, Weiss establishes that at 2200BC a severe short term drought occurred which coincides with de-population and the fall of the Akkadian Empire. Increase in carbonates in the soil and changes in soil structure indicated reduced moisture levels and enhanced evapotranspiration.

Weiss identifies 2 key phases which overlap with the collapse of the Akkadian Empire. The first phase demonstrates slightly reduced moisture levels and reduced precipitation, inferred from changes in river flow in the Tur Abdin region. Although only minor changes, the Akkadians failed to implement mitigation approaches and so when conditions became more severe, little could be done.

The Fertile Crescent wasn't as fertile as it used to be... Source: Able2Know

The slight changes in climate led to phase 2, which was characterized by dramatically enhanced aeolian sediment transport indicating drier and windier conditions. These dry periods were interrupted by violent rainstorms which would have increased soil erosion. This would have been problematic for the Akkadian empire as they depended on agriculture for trade and subsistence. Agricultural developments expanded into adjacent land. However these Northern agricultural areas were rain fed, not irrigation based, so declining precipitation and intensified soil erosion would have caused serious issues. The dry conditions came at a perfectly bad time when the Akkad were expanding agriculturally and experiencing quickly growing populations.

More recently, Weiner 2014 supports this argument. The article asserts that major drought events in a critical area are more than capable of causing population migration. This disrupts trade networks and can have cascading effects, including war. 

When keeping in mind all the articles mentioned on this topic, the most plausible explanation for the collapse of the Akkadian Empire seems to be a combination of a drying climate with inadequate leadership response and social tension. Despite the drought event posing serious problems, other small populations managed to survive this change. Perhaps if the Akkadians had responded swiftly and efficiently to the drought, by controlling population migration and managing water resources, the civilization may not have collapsed.