Why are All My Disciples Demon Lords!

I am Lin Ran. I used to be a traveller from an alternate world. I wanted to lead an exciting life, but ever since I contracted with the Most Powerful Disciple System, I had to nurture ten excellent disciples within one hundred years!
After I died, my body did not rot. Until one day when my tenth disciple achieved great things, I was finally resurrected.
Furthermore, I discovered that my ex-disciples had taken over this entire world! My first disciple founded the Xuanyin Sect, and was the leader of all the demons that numbered in the tens of thousands! My second disciple wielded the God-slaying Sword, and could annihilate a city overnight!
My third disciple was unrivalled in the world of medicine; however, he only poisoned others and never saved anyone! As for me, in a baffling turn of events, I was hailed as the Demon ancestor, the founding father of the Demon Faction, the cruellest person in the eyes of both Demons and Deities alike.
They hailed me as a Demon Lord who forged a new age. However, I was stunned. Why were all my disciples Demon Lords?!