This is about godly leadership. It’s written as an example and manual, all this detail is extra to the kings narrative, so it shows the distinct purpose of chronicles.
Jehoshaphat is sincere and has a heart for God but misguided about what he should achieve as king. A prophet redirects him.
He stops trying to make an alliance with the North, he clearly had reunification ambitions. It was once God’s aim but not any more.
He focuses on traveling about his own kingdom encouraging his subjects to godliness, a sort of itinerant preacher like Jesus.
And he sets up a system of justice which is fair and impartial. There are religious and civil branches.
It’s a resizing of ambition, letting go the glory days of Solomon’s reign, they aren’t coming back, and living a useful godly life in the new reality.
An incredibly useful leadership lesson, for churches especially. Interestingly, top of the list after preaching the word was a concern for justice.