Testing the Combination of Anti-cancer Drugs Mosunetuzumab, Polatuzumab Vedotin, and Lenalidomide for the Treatment of Relapsed/Refractory Diffuse Large B-Cell Lymphoma

Inclusion Criteria: * Patients must have histologically confirmed DLBCL NOS, high-grade B-cell lymphoma, or transformed indolent lymphoma as per the World Health Organization 2022 criteria * All patients will have relapsed/refractory DLBCL after 1 or more prior lines of therapy with the exception of patients receiving CAR T in second line that have a D score of 3 at day (D)+ 30 through D+ 90 * Patients who progressed/relapsed after prior polatuzumab vedotin are allowed * For the expansion cohorts only: cohort A must have Deauville score of ≥ 3 with the first 90 days) after standard of care chimeric antigen receptor (CAR) T-cell therapy; cohort B- other patients with relapsed/refractory after 1 or more prior lines of therapy (e.g. relapse after Day 90 from CAR-T, or relapsed after other therapies and were not considered candidates for CAR-T) * All patients that have failed 1 line of therapy will be eligible with the exception of a 12 patient cohort (A) that will require prior CAR T therapy * Measurable disease by CT or PET scan, with one or more sites of disease \>= 1.5 cm in longest dimension * Age \>= 18 years * Because no dosing or adverse event data are currently available on the use of mosunetuzumab in combination with polatuzumab vedotin, and lenalidomide in patients \< 18 years of age, children are excluded from this study * Eastern Cooperative Oncology Group (ECOG) performance status =\< 2 (Karnofsky \>= 60%) * Life expectancy \>= 12 weeks * Absolute neutrophil cou…