Backpage was founded in 2004 as an alternative advertising webpage. Soon it became the most important and biggest page for selling and buying sex. Beginning with 2011 the FBI was having an eye on the website, until it seized the website in 2018. The US Department of Justice ruled sentenced sex traffickers to prison sentences. Also, in 2018 the company Backpage pleaded guilty to human trafficking.
However, Backpage keeps its licences since not all the content was adult related.
The problem is that the demand for similiar pages is high and if you google the keywords “backpage” and “trafficking” you find lists with alternative sites.
What you can do is to alert Google whenever you come across a website that advertises adult content. So keep your eyes open and don´t look away.