In history and politics, there is little cause and effect or planning linking the two. Events rarely cause anything, it takes a benevolent, or incompetent, or, very often, opportunistic actor for the events to have any effect at all. The Helvetians' relocating didn't cause anything more than some local uneasiness, it took an opportunistic and indebted Caesar to use it as an opportune excuse to invade and subdue Gaul and make some cash. The Helvetians' moving house can't be said to have been the cause of the Gallic Wars, it was just an event somebody took advantage of. WWI wasn't caused by the assassination of Archduke Franz Ferdinand, but by the incompetent, panicky and opportunistic reactions of several state leaders, one of whom was slightly potty. WWI could easily have been prevented at that point, the supposed cause of WWI by itself caused nothing but the death of Franz Ferdinand. The so-called causes are often nothing but random events without much effect until somebody somewhere decides to act upon them in some way, which is why you can't predict the effects causes have; the presence or absence of an opportunistic actor is also a random factor, as are their intentions. There are no automatic chains of events, it is not physics.