There is a real distinction and the counterfactual test gets at it.
A condition is something whose absence would have made the event unlikely but which was present for a long time without producing it. A cause is something whose absence would plausibly have changed the outcome at the time it happened.
Tension between the European powers was a condition in 1914. It had been there for decades without producing a general war. The July crisis and the specific decisions taken in it are candidates for causes.
The reason this matters for marks is that listing conditions answers a different question from the one asked. If a condition was present for thirty years, it cannot by itself explain why the thing happened in one particular year.