There are more than 1 ways to make money with KDP. I will list them all.

1). Publishing your own books
2). You can publish other peoples book like a Publishing house.
3). You can publish Low content and no Content books
4). You can Publish Public Domain books
5). you can promote affiliate products through your books. it’s easy to do in Kindle.

Once you learn the art of making money from KDP, You can create your own course and sell it online.
Another way of earning from amazon KDP is to Produce 30–40 books, promote them online ( through ads, fb and google adsense), when you are making $5–10k a month, Sell that business for about $100k ( or whatever you think is the best price for you).
I teach people on how to make money from Amazon KDP. Email: kendrickking3581 @gmail.com for more information