The city of Fatima has been around for a long time. It was named after one of Muhammad’s daughters; I believe she was perhaps closest to him.
Anyway, I don’t think Fatima was a famed city prior to the Marian apparitions but it was significant. This is perhaps a key reason for why God allowed Mary to appear there. For one, Our Blessed Mother’s message was important to 20th and 21st centuries especially since respect paid to Mary by Muslims and of course to Fatima is bridge. For example, Archbishop Venerable Fulton Sheen always held that Mary (especially through this apparition at Fatima) would play an important role in bringing Muslims to Christ.
I wish I could add more but I’ve not studied apparitions much.