Given that the law was passed two weeks after they were married I think it has already been drafted and the whole subject was probably one of much debate. Also note three neighbouring states passed laws at the same time.

It seems likely that someone said "find a story about under-age marriage for our front page", and these two hapless yokels (or should I say Johns the hapless yokel) were the only ones stupid enough to have their photos taken.

In summary, I think society was working up to passing a law like this, and these two had a bride that was younger than most and got married at the right time.

That said, the author has definitely tried to imply that this sort of marriage was commonplace in the 30s, when it was probably at most "unusual".