In short
Jesus’ earthly ministry (teaching the gospel of the kingdom and healing the sick) shows how his work brings redemption and its blessings. Healing all diseases shows him reversing the curse on sin.
The two main elements of Jesus’ ministry, that is, (1) proclaiming the gospel of the kingdom, and (2) healing the sick, highlights the redemptive nature of his work and the blessings it brings forth. It is striking that at the start of his ministry, Jesus was quite popular with the masses and they willingly followed him, which stands in stark contrast to the end of his life. That he healed all illnesses is particularly significant, since illness, as the result of sin entering the world, here represents the consequences of sin in general.1
23 And he went throughout all Galilee, teaching in their synagogues and proclaiming the gospel of the kingdom and healing every disease and every affliction among the people.