If I had to attach one theological concept to the book of Ruth it would be the idea of PROVIDENCE.
DIVINE PROVIDENCE -is God’s ability to perpetually guide and govern all of creation in such a way that His ultimate ends are realized. Providence must be understood in the context that God is both All Powerful and Entirely Good. If he were Good by not Powerful - he would want to help but be unable. If he were Powerful but not Good he might rule like some Divine Hitler. But he is good and powerful.