Creationism was added to school syllabuses as a rival to Evolution. Creationism states that life on Earth might have been started by an outside influence.
Most Creationists automatically translate “outside influence” as the Christian God. In fact, it was that movement who successfully pushed Creationism into American education systems and who developed the argument. However, Creationism at it’s core does not pitch the Christian god angle and nor could it because then it would be religious doctrine rather than a theory.
As a result there are other versions of Creationism. The suggestion that aliens started and helped steer life on Earth is a Creationist concept.
In fact, you could argue that a Flying Spaghetti Monster started and steered life on Earth and still be a Creationist. In fact, a growing number of people are followers of the Church of the Flying Spaghetti Monster.