Christian nationalist sentiment is a product of cultural, political, and economic insecurity. This insecurity arises when the societal status quo shifts and threatens to subvert the "typical" dynamics of power. Confronted with this subversion (or its prospect), traditionally privileged groups seek to preserve the integrity of a system of hierarchies atop which they sit. To do so, they repress progressivism and ostracize societal "others," whom they perceive as a threat to usurp their own privileged position. Twenty-first century Christian nationalism—especially in the U.S.—employs "weaponized nostalgia" to accomplish this goal. Christian nationalists both inspire mobilization and justify their ideology by likening it to a mythologized version of the past, in which their worldview was still the zeitgeist. This is why Christian nationalists are so drawn to medievalism—it offers a tangible cultural ideal, and its popular portrayals have primed Christian nationalists to believe that the Middle Ages upheld the power dynamics they value. This is done in a manner that is both subconsciously influenced by pop culture medieval fantasy, and that is purposely divorced from the historical context of the "real" Middle Ages so as to better fit the Christian nationalist agenda.
Spencer Kunz (2022) studied this question.