She’s been very successful, despite being the youngest member of a celebrity family and despite growing up in front of the eyes fo millions of viewers.
(Also, she’s just been very successful, period — she’s a makeup mogul whose business could be worth a billion dollars in just a few years)
Life of Kylie didn’t get the best ratings.
There are no guarantees that it will be renewed for another season, no matter how inexpensive reality shows are to film.
Part of that is because the popularity of specific types of reality shows waxes and wanes.