Paradis was on the right track.

To make a long story short, prior to the 1880s, the AoC in Britain and the U.S. was said to be 10. But as that decade started, a yellow journalist native to London named W.T. Stead wrote a series of highly sensationalistic moralizing articles referred to as his "Maiden Tribute" series which claimed--without any real evidence--that a large proportion of prostitutes working the London streets were under 16. It caught the attention of the nation, and the moral panic quickly spread to the U.S., and from there across the West.

This occurred at a time when the Industrial Revolution was fully evolving, with one of its consequences being a reduction of labor rights for younger people as the influx of adult women into the factories and the emergence of labor unions caused them to support any measure to push younger people out of the labor market. The laws acted in accordance with this rapid infantalization of younger people. It's thus no coincidence that the AoC laws as we know them today, the schooling system becoming mandatory, and the first major wave of laws restricting youth labor (other waves would follow, including one in the 1920s that brought the situation largely "up to speed" of what we see today) all occurred starting in the same decade. And it was no coincidence that the rise of the Industrial Revolution and its myriad societal side effects created the political climate that made it all possible. It actually combined with the moralizing effects of late Victorian society that began replacing females in general with the "child" as the cultural conception of inherent innocence that was "free" from all the icky turmoil that comes with sexuality. W.T. Stead was able to take advantage of the resulting climate to create a political situation where politicians and moralists of the time had both the inclination and the power to impose all of these restrictions on younger people in virtually one fell swoop.

By the turn of the century, the concept of the adolescent was introduced to society by G. Stanley Hall, a psychologist who was using theories that have since been debunked. This resulted in the extension of childhood further and further as the 20th century progressed, with increasingly older kids entrenched in the schooling system and out of most aspects of the job market. As a result, the rationalizations by the law to increasingly raise the AoC law progressed apace.

As you can see with examples like this site ⚠️ ↗, though, the counter-backlash has begun over the last decade, and now evidence is emerging that increasing numbers of people are beginning to question this situation.