The Sudden Schools of Awakening
There are schools of awakening, what I term the “sudden awakening schools”, particularly in some Zen (Chan) traditions from China and Korea, and in some interpretations of various “Hindu” traditions (realizing this is a huge and disparate category)—this is not a complete list—which say that awakening happens in one big shift and that’s basically it, regardless of exactly how you define “it”. They deny claims of the progressive schools (Theravada, Tibetan Buddhist, some other strains of Zen, most schools of Sufism, Kabbalah, other Western traditions, etc.) that there is mappable territory before awakening and during the process of awakening and deny that there might be lots to do after stream entry or whatever you want to call it. Possible explanations for these schools include that there may be a few rare individuals who manage to go straight to something that feels to them like a complete or final awakening due to whatever interesting way they are wired or how they practiced due to whatever remarkable excellent causes (with training and meditative accomplishment in previous lives being the stock Buddhist explanation). While I have never met anyone who did this, there are various accounts in our times of it happening, though I suspect that careful questioning regarding what happened before and after would yield at least a somewhat predictable progression. This is purely my own speculation based on familiar patterns.
There may be schools founded or influenced by people who got to the first stage of awakening (stream entry) and somehow never realized there could be anything more than that or got trapped in a lie about being fully awakened when they hadn’t yet realized there was more to realize and never retracted their initial and erroneous claim.
It is possible that they went through a progression of stages but their definition of enlightenment was such that only some final shift met their criteria, such that they deny, dismiss, or fail to acknowledge the various shifts and previous causes that got them there and instead focus only on the “final” one.
There are people who just thought that sudden awakening was the single dogma that must be believed and stuck with it regardless of any issues of having insight.
There are likely other explanations I haven’t thought of or run across.
Being that every single accomplished practitioner I have ever known has followed a progressive path, including myself, it is very hard for me to believe the sudden claims except for remaining open to the possibility that there may be the exceedingly rare practitioner who occasionally manages to pull this off and thus imagines, based on their limited experience, that this is how it happens in general. In short, if you manage to do this, more power to you, and please let me know. Otherwise, I would bet on the gradual, progressive schools, and if you attain something that you are pretty impressed by, give it time to see how it holds up when life’s inevitable vicissitudes come knocking at your door over the months and years after that grand shift of perspective. Most of the people I know who are deeply into this stuff have reported many shifts and experiences that were quite impressive for some period, but later revealed aspects that could still use some maturation or improvement.