Kadampa is not a cult. It’s a religious organization that teaches Buddhism from the books written by Geshe Kelsang Gyatso. He translated the original Tibetan texts into English. His teaching lineage is over 1,500 years old, which means religious masters have an unbroken tradition of training monks and new masters since 500 AD.

The Buddha lived 2,500 years ago, and written accounts of his teachings are written in Pali that has been translated into other languages. That’s to say that Buddhism lacks an text like the Koran written directly by the prophet. Thus you have translations written by masters who passed their knowledge in long oral traditions. This is why Kadampa Buddhism teaches from Gyatso’s books. If you could read Tibetan, you could find other lineage teachings, like the Dalai Lama.

It’s sad that you didn’t find what you were looking for. But what you stumbled upon was not a cult.