Go back and listen to some of Dennis Allen press conferences. He went on record saying it took almost a month on figuring out how to use MJ effectively.

Stats don't tell the entire story on players, however according to PFR (pro football reference) Jenkins was statistically better than Bell in almost every category for 2020.

I'm not in those film study meetings, however one would believe the coaches may have felt VB was "limited" (INT's, TFL, QB hits etc) in his ability at the SS position. If you go back and look at his over all body of work, there was repetitive communication issues & rarely able to make an interception to change momentum. Not all on him however adding a veteran prescence helped the defense last season.

Not knocking the contributions Vonn made here, however Malcolm was a needed improvement in 2020.

Allen seems to try to mold the secondary to make Jenkins not look like bringing him back wasn't a mistake, it was and is a mistake. Jenkins really is the same old Jenkins while he was here the first time just older and slower. SS is a big concern in the backfield last season and this season.