Historically a number of wars have been purely based on personal choice. That comes with the territory of high power concentration(monarchies) and expansionist desires.
But in the not so distant past a lot of wars revolve around gaining control of resources. The global supply chain is a very new thing. It has changed the balance of value from being overwhelming material resource dependent to knowledge/skill based in the last few decades.
That has drastically changed the economic value proposition of war. It’s now more expensive to buy ale a countries resources by force than it is to integrate them to the supply chain.
But political tensions still exist and modern war tends to involve a lot more but in because they center on ideological disputes rather than looting.
Honestly I think Russia or North Korea are most likely to be the spark that starts the next world war. Both are basically insignificant on their own but they could force China into a conflict. Presently China, the EU, and America are the only actors whose participation on opposite sides of a conflict would change a regional war into a world war. While China has some expansionary tendencies as long as they left japan and South Korea alone they would avoid mass conflict and they are aware of that. But Russia’s international meddling or North Korea could force their hand.