All answers are wrong.
The kardashians capitalized off of timing.
Before Kim Kardashian there was Paris Hilton who was shaped like a 5 year old boy, racist, and the personality of a stuffed animal.
Kim is the exact yang of that yin. She was exotic looking loves minorities and had personality. She was also Paris hiltons assistant. Eventually got her own show and played the extremely dumb girl on E network and then with the indirect help of Ray j releasing the sex tape of Kim without her permission, kims mom sued which made her more popular and more rich because they eventually were paid off from the company who was selling the sextape.
Ryan Seacrest became involved eventually and it was a done deal. Ryan is more powerful then scooter Braun or your LA Reid's at this point.
The rest is history.
Tl:dr = Timing is everything