No wonder these guys scam folks... There's little consequence. He's was one of the rare ones to even be criminally charged.
I don't think Abdallah's necessarily off the hook. They may have missed out on rearresting him before his probation was over, but they may still pick him up. After all, the SEC's done the necessary investigating, and will get more information in discovery. It'd be an easy case for the DOJ to make.
The SEC worked with the DOJ in the first case, and probably kept them informed of what was going on with their new investigation.
This kind of like the Durante case. With the help of a relative, Durante laid the groundwork for his new scam while still in prison. Upon release, he set it in motion. Six years later, the SEC and the DOJ moved against him pretty much simultaneously.