The main reason why it is called the Gap Theory is that this theory suggests that a catastrophic event occurred during the time between Genesis 1:1 and 1:2.
There is a huge question among various scholars about why the earth was described as “formless and desolate” in Genesis 1:2. So they came up with a theory that there was probably a “fully functional earth” that was filled with all living creatures which includes those extinct dinosaurs.
However, this earth was unfortunately destroyed due to Satan who was one among the “fallen angels” who rebelled against God. When God casted him out from Heaven, Satan fell down into the earth which caused such tremendous impact that it completely devastated it. As a result, earth became “formless and desolate”.
Since earth got destroyed, God had to restart and create again everything starting from the ruined earth.
Some Flaws of the Gap Theory
In my own personal opinion, this Gap Theory did not really happen since there is really not enough evidence to support the catastrophic event. If it did then it would have been recorded as well in the Book of Genesis rather than leaving us all trying to speculate and come up with ignorant hypotheses.
Another flaw that I saw on my own personal perspective is the “light”. God had not created light yet until Genesis 1:3. You have to know that light is very important for the survival of all living creatures here on earth. Without it, it would be impossible for them to live and thrive unless Satan destroyed it as well when he got casted out.
Perhaps the real question here is, “Why was the earth from the very beginning of God’s creation of the world referred to in the Holy Scripture as “formless and desolate”?
Again, the answer to this question is based on my own personal opinion only. If God Who is our Almighty Creator wanted to create earth in an instant, then He can do so by simply giving His powerful command. As a result, everything is going to be completed just on the first day.
However, there is a reason why God had to do it in a step-by-step manner. God probably designed everything here on earth to be formed or created in a manner where it will take some certain amount of time. A good example are the plants and animals. They actually do need some time to grow and reproduce. This is probably why God had also started redesigning earth from the scratch.
Moreover, there is no such thing as a time gap that occured between Genesis 1:1 and 1:2. God’s creation of the world from the very beginning was continuous without any interruptions. One of the main reasons why the Holy Scriptures have to describe God’s detailed creation of everything is to demonstrate His Power which makes Him worthy of being served as our only One and True Almighty God.