No, you can't change people's habits and it's a waste of time to try to do so. Some KU readers do buy books but many don't. They either can't afford to or they read way too many books to buy each one separately, this is why they are in KU. You are right that KU readers and buyers are a different audience but KU readers are now the new library readers. You always had a chunk of readers who never bought books but turned to the library instead.
Focus on what YOU can control. If you want better sales, do your best to get things going.
Lower your prices and run some promotions. Then raise your prices so you can make more per book. Write something new if you haven't in a while. Keep promoting your backlist. Do some mailing list swaps. If you are on BookFunnel or StoryOrigin, do some group promos. Start work in a new genre. Write something trendy to get money rolling, write some erotica, use your KU free days and promote the heck out of them. Try submitting to serial apps like Radish, etc., so you can have extra money come in outside Amazon. If some of your books are lagging in KU then you might wanna try going wide with those and see how you do.
But, don't waste time thinking you're gonna convert all the KU readers into buying books. Won't happen.