Why did fighting on the western front of ww1 become a stalemate with high casualties but little progress

World War 1 had a lot of trench warfare. Opposing sides would set up trench networks and hide in them. Some would try to lead frontal assaults but would be shot down as they got closer to the other side. As this happened back and forth, nobody could win it was a stalemate. At the same time, a lot of people died in attempts.