If the map was the only evidence then the possible cause of World War I would be the alliances formed in Europe in the early 20th century.
How did alliances cause WWI?
The existence of alliances created a situation in which conflicts between individual countries could quickly escalate into larger, more widespread conflicts.
When tensions arose between two countries, their alliance partners would be drawn into the dispute, turning a bilateral issue into a multilateral one.
Alliances were initially intended as defensive measures to deter potential aggressors. However, they often had the opposite effect of making countries feel more secure in their aggressive actions, believing that their allies would support them in a conflict.
This entanglement of alliances led to a dangerous arms race and a willingness to engage in risky actions.