There may be many reasons, but here are two key reasons that Jesus performed miracles.
One key reason that Jesus performed miracles was that He loved people and wanted to see them healed or set free or delivered!
In one case, His friend Lazarus, Lazarus had already died. Only a miracle could bring Lazarus back to life; so Jesus performed a miracle and Lazarus was raised from the dead and restored to his sisters.
In other cases, people were lame, or blind, or had suffered from diseases for many years. Jesus was moved with compassion and reached out and healed them.
A second reason why Jesus performed miracles is to demonstrate God's power and that He is God. God is the creator of heaven and earth; He has all power over creation. God can perform miracles.
Jesus demonstrated that power and it is one way He showed that He came from God and He was -- and is -- God. He has power over sickness and death; He can walk on water and raise the dead. Jesus truly is God!!