For that matter, the New Testament wasn't written until long after the life of Jesus, the canon wasn't established until long after many oral traditions were, and some of Old Testament canon the status of "deuterocanon/apocrypha" has been controversial.
Religions start with key important figures, events and practices long before they get encoded as text. The only one I can think of off the top of my head that might have gone somewhat in the reverse direction was L. Ron Hubbard writing Dianetics and other books to develop a schema and theory for psychological healing before he officially started Scientology. But I don't know all the details about early Scientology so it's hard to say precisely how much was pre-encoded there. I've heard rumours that Hubbard was involved in Freemasonry before starting Scientology so if it's true, it's likely that some of his experiences in it shaped his writings. I also heard that Paul Twitchell, founder of a lesser-known group called "Eckankar" spent some of his earlier days in Scientology. But I digress.
When you strip practices away from dogma in an attempt to further enrich corporations, it's almost like trying to start over with the practices borrowed from some past heritage, the corporation's leadership as the key figures who give advice or select practice consultants to confer with, and with some milestone of success as the promised "awakening event". It definitely runs the risk of turning the corporation into a personality cult where your boss directly or indirectly tells you how to reach a spiritual objective... Of making them money.