It was not the 'cornerstone' for many. There are other parts of the Noble Eightfold Path, after all. And there are many 'Dharma doors': devotion, faith, charity, compassion, ethical behavior, the path of study, the path of shamanism, the path of work, the path of yoga, lay and monastic paths, social and hermetic paths.

But one historical factor was that in the effort to establish, preserve, and study a ratified canon of scriptures, focus on the letter rather than the spirit of the teaching sometimes took precedence. Some radically meditative schools arose in response.

Millennia later, Zen set root in America before most other Buddhist sects, in part because western Buddhism is made in the image of the Western mind: heavy on the intellectual, light on the empathetic and physical, and always with the question "what's in it for me" resounding Western individualism. The vernacular by which Asian language and concepts were conveyed was, back then in the 1930s to 1960s, the terminology of psychology and to a lesser degree of atomic science.

Because Westerners are head-heavy, our concept of Buddhism is head-heavy. The common person generally thinks it's about meditation, but more fundamental concepts like compassion and faith are not widely embraced, largely because that's not what our culture recognized and glommed onto when Buddhism arrived here.

But outside of pop Buddhism, there are vibrant and authentic practice centers, and second and third generations of Western Buddhist masters unfolding a uniquely Western Buddhism without losing the grounding and lifeblood of lineage.