Used to be, there was this physics prof who taught his students about gravity. His name was Galileo. It took the Church something like four hundred years to admit that he was right and they were wrong.
The creationist movement in the U.S.A. is an anti-science movement. The theory of evolution is their first target because it is low-hanging fruit. Theories of gravitation do not contradict the Bible. The theory of evolution not only contradicts the Bible, it contradicts the very first chapter of the Bible—possibly the only chapter that some Christians actually manage to read all the way through before they get bored and put it down.
Attacking the theory of evolution is more meaningful than attacking theories of gravity, but if they were allowed, they would take us back to a day when nobody understood gravity, or lightning, or rainbows, or the origin of species, or anything else that was not revealed to them by their leaders.
Religions exist because people want answers, and science exists because people want answers. Some people (a lot of people, actually) want answers _now,_ and they don't want to have to work for them. The priestly class created itself to serve that need. A few people want to figure things out for themselves. They become scientists.
When Olaf the farmer asks the village priest, "Why did God smite my barn with lightning and burn it to the ground," the priest needs to have an answer. The priest needs to know all of the rumors that are being whispered in the community (the confessional is a good tool for that), and the priest needs to be able to say, "God knows of your lust for Jennifer the baker's daughter, and nothing that you do is hidden from His eyes." or something like that. A priest who cops out by saying, "I don't know, God's ways are mysterious," is not going to last long in the priest business.
So, lighting becomes a symbol of God's wrath. And then along comes somebody like Benjamin Franklin who says, "put one of these on the roof, and your barn will be safe from lightning," and all of a sudden, the priestly class is embarassed. The priests have a strong incentive to make-up and proclaim explanations for natural phenomena, but any time they do it, they risk getting exposed by future scientists.
St. Augustine exhorted his fellow Churchmen to resist the temptation to explain natural things—to avoid conflict with science. But the majority of religious leaders have a hard time with that. Science therefore, is an existential threat to them. They do not know how to lead people who know how to think for themselves. They only know how to lead sheep.
The creationist movement in the U.S.A. expresses the frustration of petty priests and preachers with a world in which school kids are taught to think like scientists. They want to stop it if they can.