Could king Saul have done things differently or was his downfall and slide into rage and madness inevitable? As I continue to read through the story of the early monarchy this question comes back to me time and again. By the time we reach 1 Samuel 18, Saul is torn between keeping David close and wanting to kill him. And it will get worse.
Nowhere is there any sense of Saul repenting of his sin and seeking to submit to God's authority. He just becomes more and more determined to retain the throne at all costs. He plots and schemes and it will go from bad to worse over the next few chapters of the story.
Clearly translating v10 present challenges. The NIV goes for evil spirit with a footnote and prophesying, the New Living settles on tormenting spirit and raving like a madman. But I guess the basic point is simple enough. Saul got out of step with God and never got back in step.
However you work out the complexities of what exactly is happening spiritually with Saul, this fundamental question of walking in God's ways is crucial. Surely the most salutary lesson is that a leader chosen by God can fall so far.