Of course it’s contrived in 1980. In ANH, Vader just happens to chase Leia to the planet where his son and her brother lives, and he just happens to take possession of his sister’s droids, one of which just happens to be carrying the stolen plans his father is trying to retrieve?
No. Leia is going to Tatooine because that’s where Obi-Wan is located. She’s not just passing through the neighborhood by coincidence.