Two ideas that make Buddhism both necessary and possible are karma and reincarnation. Without the absolutely inflexible regime of karma, where every deed is a cause that creates a corresponding moral effect, and reincarnation, where "you" are endlessly returned to yet another life of suffering, there would be no motive for seeking extinction through moral effort.
Yet these two ideas are, to me, impossible to take seriously. The idea of a universal moral order that is not personal makes no sense to me. And the mechanism by which either a soul (in Hinduism) or a bundle of karmic debts (in Buddhism) is grafted from one physical form into another...well, by what magic does that work?
As a psychological asceticism, Buddhism has much to commend it. How much human misery does indeed come from being attached to what is impossible. But as a religious description of how man and the world actually function? Unbelievable.
For some reason, a lot of post-Christian Westerners who recoil at the notion of a personal Deity making specific moral demands on them, demand which have consequences beyond this life, find it acceptable to talk about "the Universe" teaching them lessons and dishing out consequences. As if that is either intellectually or aesthetically better.
"But"...as the King of Siam sang
"is a puzzlement."