Many of the psalms have no author attributed to them, so we have a large group of ‘unallocated’ psalms that were written for (or of) the descendants of Korah.
Psalm 43 was written by someone in a position of being under attack and needing to rely on God for deliverance.
It could easily be something Hezekiah would have prayed when faced with Sennacherib’s invasion of Judah and his threats towards Jerusalem.
Vindicate me, O God, and defend my cause
against an ungodly people;
from those who are deceitful and unjust
For you are the God in whom I take refuge;
why have you cast me off?
Why must I walk about mournfully
because of the oppression of the enemy?
O send out your light and your truth;
let them lead me;
let them bring me to your holy hill
and to your dwelling.
Then I will go to the altar of God,
to God my exceeding joy;
and I will praise you with the harp,
O God, my God.
Why are you cast down, O my soul,
and why are you disquieted within me?
Hope in God; for I shall again praise him,
my help and my God.