If one accepts socionomics, negative social mood caused these wars along with their alleged causes. In other words, the wars and the believed causes for the wars had a more fundamental, non-deterministic but hard to resist, holistic cause that is not apparent, appears to be an effect rather than a cause, which can be traced and even predicted by looking at social, in particular market, behavior.
Social mood, however, is not well defined except to say what it is not. It is not the market changes themselves. It is not political decisions. These are all effects. So, ontologically, it is not clear what social mood is. What makes it worth considering is that socionomists claim they can assign likelihood to future changes in social mood that affect changes in political, social and market trends by studying patterns of social mood displayed in "sociometers" such as market charts. The reason market charts are useful is because of the large quantity of data available that appear patterned rather than random. The market patterns socionomists value are called Elliott Waves.
The efficient market hypothesis (EMH) provides an opposing interpretation of these market charts by calling them random walks. For EMH social mood is an effect, not a cause. If the EMH is right then social mood would not help in finding the causes of the world wars.
However, assuming socionomists are right, and they do show enough success in market predictions that traders are willing to purchase such predictions and learn the patterns themselves, socionomics or Elliott Wave analysis could provide a way to predict when a future war is likely to occur as well as why the world wars in the past occurred.
To see how such analysis might help explain world wars, here is a video showing a socionomics analysis of Korean politics and the KOSPI (Korea Composite Stock Price Index). Although political changes in Korea and the market chart are compared, both the market and the political changes are assumed to be caused by a holistic cause of something called social mood that changes in a patterned manner.