Saul at first did what was wrong, disobedient.
Then he ended up going to a medium, which is possibly some sort of divination person.
So, the disobedience in one way could have been connected with producing the disobedience in the other way.
So, this could show that the two are connected. Starting with one, he wound up with the other. There is "the spirit who now works in the sons of disobedience," our Apostle Paul says in Ephesians 2:2. Satan's same evil spirit produces the disobedience of rebellion and of divination, and ones can see the degradation this selfish spirit causes in people, in one's character and emotions and personality.
Saul, in disobeying, kept getting worse and worse and worse, including in fear even while taking action to control his kingdom, with many cooperating with him > yet, he kept being able to act in fear. So, there is fear which somehow comes with both, also.
But divination was possibly thought to be an obvious sin. And Samuel possibly meant to show how disobedience, though not obviously like divination, still was very displeasing to God . . . in how He sees things and feels. And perhaps Samuel was telling Saul how Saul in disobeying could be on his way to also sinning in divination; and at that time, possibly, Saul was thinking, "No way could I do something that bad!" But after getting started, he did go on to that.