The plagues that YHWH brings upon Egypt are a direct assault on the tradition of Egypt and its religious system. Each time God causes something traumatic to occur it is in direct opposition to one of the gods. This is to demonstrate that YHWH is the one true God to both the people of Egypt and also the spiritual being who has been in rebellion against God for centuries at this point, thinking they've been holding the upper hand. What God is doing here is going to echo across the ages and the world will know that there is one true God above them all.