Aside from hyperbolics about trench warfare, how the first world war evolved into trench warfare is interesting in that the generals and planners weren't retarded. It devolved into trench warfare because nothing else could be done at scale. There was actually quite a lot of modern warfare, but it wasn't able to be done at a scale to effect anything. So Machine guns and artillery were the only thing that remained effective at scale. And they were both primarily defensive, meaning that you could just sit in front of each other with your army, and digging in was the only choice. Which meant that the only way to dig them out was with infantry, and enough infantry at one time to overwhelm them. And the counter to that was trench systems and depth.

The war was a natural progression, it's not like generals in funny hats smoked opium and thought it'd just be grand to make as much mud holes as possible.