At the beginning of the week of His crucifixion, Jesus presented Himself to Israel as their King. He came meek and lowly, riding upon a colt the foal of an ass (Zech 9:9; Mat 21:5). He was the promised Messiah, the King. Yet, His people rejected Him. Rather than being elevated to the throne, He was lifted up on the cross, where He offered Himself as a sacrifice for the sins of His people. During the Passover week, the rejected King was continually before His people for their examination, for they needed to see that He, the Lamb of God, was truly without blemish.
In their ignorance of scripture, and dullness of sensitivity to the Spirit, they did not know who He was, nor did they understand what He was doing. But He knew. He wept over the unreceptive hearts of His people and in anticipation of the judgments that would come upon them.
During that last week, Psalm 21 must have brought great comfort to Him. Its placement, immediately before "the Psalm of the Crucifixion" (Psa 22), is more than coincidental.