7/10 Americans are Christian[1]
So, there are around 210M American Christians on FB.
So, these posts reached roughly 60% of Christians. Sounds feasible to me. Top brands in a niche like Christians can get broad reach.
[0] https://www.statista.com/statistics/408971/number-of-us-face...
[1] https://en.m.wikipedia.org/wiki/Christianity_in_the_United_S...