Why do some people find something easy and other difficult?
Many factors come into play.
But mostly, a subject or topic, where we have no interest is usually difficult.
Some people will say lack of knowledge makes a subject difficult.
I think a sweet comobination of both is needed to make a subject or topic easy to understand.
Interest cannot develop without knowledge. How can you get interested in a cricket match if you don’t know about the rules or scores. You would rather choose to watch football, if you understand it.
the more complex the system, the lack of knowledge will play bigger role. And on flipside, the more the knowledge, the person will be more interested in that system.
So to make something interesting, check if the person has any knowledge or required enough knowledge about the subject.