This answer is from Trinitarian perspective shared by the 3 mainstream branches of Christianity: Roman Catholic, Orthodox, and Protestant.
This article succinctly shows how Jesus in His human nature needed the Holy Spirit power especially at critical junctures of His mission on earth. The anointing at the Jordan river's baptism signified God the Father revealing Jesus to be Messiah and the Holy Spirit empowering Jesus in His human nature for the role. See another article discussing the relationship of Jesus with the Holy Spirit.
Jesus as human being was conceived by the Holy Spirit, so the human nature Jesus already had the Holy Spirit since birth. The anointing at baptism didn't imply that the Holy Spirit was not yet given by the Father, but more of empowerment, probably similar to how we as believers can, sometime after baptism, be given spiritual gifts for ministering to the body of Christ. Jesus did not sin before baptism, so technically He didn't need to be baptized. The baptism was the occasion chosen by God the Father for the unveiling.
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Your link cited Jesus said "the Spirit of the Lord is now upon me". Does it mean before baptism the Holy Spirit was not yet present?
the context was Jesus preaching at the synagogue in his hometown, Nazareth: Luke 4:14-30. This was after his baptism / annointing. Jesus was announcing the fulfillment of Isaiah 61:1-2. He was referring to the empowerment mentioned above. It is safe to assume that throughout the many villages and cities he visited before his crucifixion, he made similar announcement because people needed to know the good news of the coming Kingdom of God and Jesus taught them how to respond (i.e. by repenting, believing, and then living according to the ethics of the Kingdom).