Alfred Wegener created the theory of continental drift primarily to explain the observation that continents appear to fit together like pieces of a jigsaw puzzle and to provide a rationale for certain geological and fossil evidence, such as the distribution of glacial deposits, coal beds, and similar plant and animal fossils found on widely separated continents. His theory posited that continents were once joined together in a supercontinent called Pangea and have since drifted apart over geological time.
So, the most accurate answer to your question is:
To explain Pangea and continents moving apart.