If they thought that backpage enabled/induced trafficking, then them being a top source of tips isn’t that valuable.
Would you let a drug dealer run a meth lab if he reported his customers for prosecution?
You can argue with my analogy, and I don’t quite agree with it myself, but I can see the government seeing it that way.
As I recall, the FBI did exactly that fairly recently, when they pwned some credit card trading site and ran it themselves for years.
"Playpen was a notorious darknet child pornography website that operated from August 2014 to March 2015.[1][2] The website operated through a hidden service through the Tor network which allowed users to use the website anonymously. After running the website for 6 months, the website owner Steven W. Chase was captured by the FBI. After his capture, the FBI continued to run the website for another 13 days as part of Operation Pacifier." -- https://en.wikipedia.org/wiki/Playpen_(website)
I don't agree with "entrapment" arguments and "faciliting spread" here. The site was already up, and the users were going to go there regardless. Running it for a week or two more is at worst marginal harm, considering it was already there for a good 6 months.
A major escort site (not BP) was ethically ran by a retired sex worker. The site sold out of fear of prosecution and the new owner is a horrible person in my opinion.
half the government wants to keep sex work illegal and doesn't really want to stop trafficking that much.
This reads oddly, since in the government context "sex trafficking" is synonymous with "prostitution".
The only reason for the government to see it that way is because someone powerful wanted them to.