They can’t dig a trench. The water table is often above the natural ground level, and their pads are only a few feet above that. When starship dug that hole, water seeped in and partially filled it!

But it is the same thing at the cape - but there they brought in soil and built up the land by something like 10 meters, and built their pads and trenches in that. Moving in that much dirt would take years.