The Spirit of God (YHVH) is speaking to David, and calling David the Lord to be i.e Messiah; as straight after it appoints him as being of the Order of Melchizedek (Psalms 110:4).

In Psalms 89:19-21 David is appointed as a holy vessel to be the anointed (Messiah) Arm of the Lord; which we see paraphrased in Isaiah 52:13-14.

When the Spirit of Salvation (Yeshua) is placed into the flesh of David (Isaiah 52:10), it is just the language barriers that make it confusing; especially them changing his name into a swear word (H5580 jesus = shall be a beast & G5580 psudeo-Christos = false Christ).

It is like when God spoke at Yeshua's Baptism by John, it says "This is my beloved (David) Son, in whom I am well pleased" (Matthew 3:13-17; Mark 1:9-11; Luke 3:21-23).

There are multiple places in the Tanakh, David is ultimately the Messiah over the Messianic Age; so Yeshua has to be David with the Spirit of the Lord upon him.

Ezekiel 34:23-24, Ezekiel 37:24-25, Jeremiah 23:5, Jeremiah 30:8-9, Jeremiah 33:15, Hosea 3:5, Isaiah 55:3, Isaiah 22:22, Isaiah 9:6-7, Revelation 5:5, etc.