The answer is: Didn't want to spoil inheritance

Ruth 4:5-6

In the Book of Ruth, we delve into the complexities of family loyalties and inheritance laws in ancient Israel. When a kinsman refused to marry Ruth, it's a bit more than just personal feelings; it pertains directly to family land and heritage. This kinsman, identified simply as “the closest relative,” was looking out for his existing inheritance, afraid that marrying Ruth and supporting her late husband’s lineage might complicate his own future as a landowner.

This story becomes an interesting lens through which we see human concerns around family, legacy, and social obligation. Interestingly, the concept of the "kinsman-redeemer" or "Goel" was super significant in the Israelite culture. This framework included not just marrying a widow but also ensuring family continuity and protecting one's tribe’s land, a vital aspect for survival in a mostly agrarian society.

But wait, there’s more! Right in the middle of this tale, we see this remarkable reversal. Boaz, a relative but not the closest, heartily steps in. He agrees to redeem Ruth and take her as his wife, showcasing qualities of generosity and compassion – ultimate ideals known to resonate throughout many texts in the Bible. Ruth's journey from a Moabite widow to the great-grandmother of King David shows how unexpected journeys can lead to incredible ends and how redemption often blooms in the unlikeliest of places. Isn’t that a compelling peek into divine providence?