Ironically, Hanukkah is found in Christian Scripture in 1st and 2nd Maccabees, but is not found in Jewish Scripture at all. Why? Well, these two books (there is actually also a 3 and 4 Maccabees, which some Christian groups consider part of Scripture, but which the Catholic Church does not) were originally written in Greek by the Diaspora Jewish community, they were never translated back into Hebrew. Because Christians preaching the Gospel among Diaspora Jews were using several Greek-language based books like Maccabees to great effect in conversion, the Jews who were opposed to Christianity ultimately ruled that any book not originally written in Hebrew was NOT part of Scripture and should not be considered sacred.
Unfortunately, this ruling meant the Hanukkah celebration was no longer a Scriptural event. This wasn't a huge loss, as it had never been a great holy day. But Christianity spread through Europe and North Africa, and the celebration of Christmas began to become a thing starting around 350 AD.
While it was considered a minor liturgical holiday for the first millennium of Christianity, by the medieval period, Christmas was a major cultural holiday for Christians. The early industrial period turned industrial nations into a surplus-goods society, in which Christmas came to be a way to showcase the cornucopia of goods Christian Europe was producing. Gift-giving entered the picture in a major way. Every culture (Asian, African, etc.) wanted to share in that new outpouring of Christian European wealth.
It was therefore no coincidence that by the early industrial period, Jews were converting to Christianity wholesale and retail. Indeed, some scholars point out that, if not for WW II, Jewish assimilation was on track to wipe out Jewish culture in Europe by the end of the 20th century. To slow the assimilation, one of the rabbinic tools was the elevation of Hanukkah to a major cultural event in order to combat the influence of Christmas. It's still a very minor liturgical event, but the cultural significance now pretty much swamps the religious significance. Hanukkah is now a way for Jews in a Christian society to celebrate Christmas without feeling guilty.