We once heard a lot of smart people say Williams would never work in the NFL again following his role in the Saints' bounty scandal. But two different organizations have given him a chance in successive years. In both cases, Williams had a personal connection.
Rams coach Jeff Fisher and Williams worked together in Tennessee, where Williams was his coordinator. (The Titans gave Williams a job as a defensive assistant last year.) Williams actually signed on as DC for St. Louis in 2012, but was suspended indefinitely due to the bounty scandal and subsequently released before ever coaching for the Rams.
The Rams' defense had dominant moments last season, but it struggled with consistency and didn't come out of the gate strong. Despite a great defensive line, St. Louis was in the middle of the pack in yards and points allowed.
Even though Williams was not a coordinator last season, he received much of the credit for the Titans' newly aggressive approach. Williams seemingly knows only one way to coach, and that is to send a lot of blitzes and different looks at opponents. Fisher, more than anyone, knows what he's signing up for.