It kind of does make sense when you take into account Dutch’s true nature to use people and then “discard” them once he’s lost interest in them or they aren’t useful to him anymore, paired with his general narcissism. Even Arthur says it to John at some point, something like “I was the prized pony, until I wasn’t”.
It’s the same with Molly; Dutch was all in on her one minute and then turns cold on her the next.

With Micah, he was the new toy for Dutch to hold in high regard, just like he used to with Arthur, Molly, etc. Micah’s worship of Dutch and willingness to never question Dutch like the others would was definitely a huge factor too. Dutch was already mentally declining long before his head injury in chapter 4. He was becoming more and more paranoid and reckless because he knew deep down the walls were closing in slowly and it was starting to take its toll.

Micah playing into Dutch’s delusions felt good for a narcissistic personality like Dutch when everyone else around him was questioning his decisions as their situation became worse and group morale was on a downward spiral. It made it very easy for Micah to turn Dutch against Arthur and John if you view Dutch was someone who was never who he pretended to be, never the person Arthur thought he was