Not a belief, just totally consistent originalism. Well known fact the founders supported interracial marriages.
This isn't about originalism. This is about the sitting judges' religious beliefs.
This is the droid you're looking for: https://www.npr.org/2022/05/18/1099542962/abortion-ben-frank...
It reiterates the thesis of the first article: "It just wasn't something to be remarked upon. It was just a part of everyday life."