Can corroborate, 2012 is when I stopped using Tor for anonymity because a lot of busts happened all in a row. Every bust had some sort of Silk Road style clearnet mistake associated with it, but parallel construction felt like the real answer. A bunch of sites that had been fine for years don't suddenly all make tiny fatal mistakes at the same time.

I'm sure any operators that didn't get busted realized the heat had showed up and chose to shut down. When you are facing 20 years in jail you don't need hard evidence that Tor is broken to decide to walk away.