How did trench warfare come to define the western front

Trench warfare came to define the western front as follows:

Trench fighting achieved its height on the Western Front during the World War I, which took place from 1914–18, when troops of millions of men fought one another in a line of trenches stretching from the Belgian coast to Switzerland via northeastern France.

One possible explanation that First World War on the Western Front resulted a enormous trench war was that Western Europe was heavily populated. The trench lines had the effect of putting Western Europe into two fortresses whose military forces were sieging one another along a single border. In the North, geography fought toward consolidation.

the answer would be a i think?