Note that the Baltimore program your article mentioned has had contraversies, but there's nothing there to show its been unsuccessful. Now I'm not saying it has been successful, I don't know, I'm just making the distinction between a program having a contraversy and a program actually failing.
Those contraversies might make program politically unsustainable, but they don't necessarily mean the program is failing on a case by case basis.
So maybe Richmond has some unique quality, better and harder working staff, better support or something. Maybe there's a better economy or a better society so people on the program have a real opportunity to get work and turn their lives around.
Or maybe Richmond's singular success is just a matter of a stats quirk, as Killkrazy suggests. The gentrification or some other thing is affecting numbers more than this program. Or possibly the opposite is true, the programs are effective but the effect isn't well captured in the collected stats.