Law enforcement was paranoid about making sure it only went to criminals. It was producing so much intelligence, any non-criminal usage wasted lots of time.

The fact that it was really only criminals using it was the big selling point.

I agree in part, but nobody legit is paying $200/month to use signal or other free secure private messengers. If it was a free platform I can see innocents getting caught, but considering it was sold by criminals, to criminals for a criminal fee — I think they were mostly correct.

Granted I’m hazy on the details of the story, but I did not recall a service fee. Just a few hundred dollars premium Android phone geared towards secure privacy. Sure, there was a nudge and a wink towards crime, but I could easily see it appealing to a civil protestor, journalist, or philanderer.

It was only available from a salesman, you couldn't order it via a website. The salesmen knew their clients, and knew they were criminals.

The sales chain was what made the operation so effective. The only people who had the phones were the ones the FBI wanted with the phones.

But there are many open source, free, and actually secure messengers...

not in the late 2010s when this was happening.

There was (is) one though, audited by NCC Group in 2015. A vuln has been found but fixed by 2016. Not sure about other messengers.