Why do Immunomodulatory Drugs such as IMiDS and Cereblon Modulating Protein Degraders such as CELMoDs stop working?

Why do Immunomodulatory Drugs such as IMiDS and Cereblon Modulating Protein Degraders such as CELMoDs stop working?
How do CELMoDs protein degraders compare to IMiDs?
What are cereblon modulating protein degraders?
What is protein degradation?
How often should imaging be repeated in someone with smoldering myeloma? symptomatic myeloma? What imaging should be done in each situation?