This one is a stretch for me, honestly. I'm willing to have my mind changed, but prepubescent nudity was pretty common place before relatively recently. Like even super conservative sexually repressed Victorians didn't really consider baby nudity to be... Nudity. Like, there's just no there there, y'know? Kinda like how today you've got album covers like that nekkid baby in the pool, or they show female babies without a shirt on in movies/on TV. Because before a certain age it's just a nonissue.
Again, maybe I feel that way because I'm not into cherubim penis? Are there people super into nekkid baby angels and I'm just too sheltered to know about it?
I wouldn't even say "before relatively recently" as it depends where you are. Up until my daughter was like 5 or so she was just fully naked or in a swim diaper at the beach and like you say nobody considered that to be "nudity".
But we're in rural Canada where we don't have the pedo paranoia that seems to have taken over America, and we just let our kids run free like we did.
Though it's growing in the cities and small towns now, not long ago in a nearby town there was a Facebook panic over a man in a white van driving slowly around town. Unsurprisingly he turned out to be a plumber looking for the right address.