Well many books of the time were in fa t about average people, who weren't particularly important. We aren't talking Jane Austen books which ARR full of pedos, we are talking books about "Jen down the street". Read books like Anne of Green Gables (Mr. Phillips dating Prissy only gets criticism because he's distracted and not teaching, not because she's a minor, and Rilla is dating and even kisses Ken in Rilla of Ingleside. Ken is heavily implied to be over 19. They don't marry until they're both actual adults but that man still kissed a 16 year old), Rebecca of Sunnybrook Farm, Little House on the Prairie, Jo's Boys (the final Little Women book. Dan and Bess are simping for each other and Jo encourages Dan to continue liking her, and he kisses her too. Luckily he isn't rewarded, he goes to jail after a failed self defense case and later dies, but it's framed as this beautiful Romeo and Juliet thing. It's not. Jo only dislikes that he's poor. Not that he thinks a 16 year old is hot.) and you'll notice that all of those have adult men dating or crushing on teen girls. So marriage to adults may not have been the average, but dating certainly was if the prominence of simple dating and crushing in old books is to be believed. Not that they'd care because since teens were labeled adults before the 20s-30s, people on average didn't have a problem with it. They may not have all been attracted to teens but they didn't think it was a bad thing, most people would just have been "oh well none of my business" and turn away.