Wiersbe points out that both Hushai and Ziba brought good things. Hushai was answer to prayer and Zibe brought things needed in the short term, but deceived David in a moment of weakness and caused problems in the long term. David knew Ziba was an opportunist and even questioned his motives; but then was probably braced to believe everyone would turn on him and believed it about Mephibosheth. Even though Mephiboseth was crippled and unlikely to lead an uprising; and had seemed genuinely moved to become part of David's household.
And why hadn't David accounted for Mophibosheth. He was supposed to be part of the family. David brought hundreds of servants, why not care for the crippled family member?
Between Satan's lies from Ziba and the continuous curses from Shimei, Saul's relative- David was being worn down. It sounds like the Shimei story is ongoing.
Here's what I was looking for.
"What did all this suffering accomplish for David? It made him more like Jesus Christ! He was rejected by his own people and betrayed by his own familiar friend. He gave up everything for the sake of his people... Like Jesus, David crossed the Kidron and went up Mount Olive. He was falsely accused and shamefully treated and yet submitted to the sovereign will of God. 'Who when He was reviled, did not revile in return; when He suffered, He did not threaten, but committed Himself to Him who judges righteously.' (I peter 2:23 NKJV)
By all human counts, Absalom had the advantages. But David had the Lord.
Because David fled, it was a bloodless coup. which is what David wanted- the people of Jerusalem protected.
Hushai's song and dance manged to thread the needle between truth and lies while still convincing Absalom of his "loyalty". He promises to serve who God chose. He says long live the king, without adding a specific name, etc.
Wiersbe points out that David would seek God's will. Either through his own prayers, A prophet like Nathan, or by using the Urim and Thummin. Absalom used a man, Ahithophel, who do not show signs of seeking God before offering wisdom, although the Bible says both David and Absalom treated his advice like the Word of God.
For me, that provides some insight into that final verse.
What a contrast in these two stories. David suffering and struggling while Absalom gets his wish with no effort. It seems unfair. It seems wrong. But that's only if you forget or never knew that there is a God in heaven, on His throne, sovereign, and whose will will be done. It's a contrast well worth remembering.