Campbell led the Terps with 10.5 sacks per game in 2020.
Brian Braswell is also joining Mike Locksley's staff as the Terps' new offensive line coach.
Offensive line coach John Reagan has also left College Park.
Lewis is the highest-rated inside linebacker in the 2021 class.
The Terps also secured wide receiver Marcus Fleming as a transfer from Nebraska.
The move was made due to a pause in team activities, which was caused by a COVID-19 outbreak.
The recruiting class is led by four-star linebacker Demeioun Robinson.
The walk-on threw for 218 yards and two touchdowns against Rutgers.
The Terps were without Taulia Tagovailoa, Chance Campbell and Ayinde Eley, among others.
“Coming out strong always gives you the momentum swing early in the game."