I didn't say it is "the" premise of Buddhism. I said it is a premise of Buddhism.
It is.
The story of Shakyamuni Buddha achieving enlightenment after 49 days of meditation under the Bodhi tree is pretty well known. There, of course, are a lot more antecedents to contemporary Buddhist thought and ethics than that one incident, but it's fair to say it's a pretty core part of the historical tradition, and precedes essentially everything that came after.
For context in this discussion, I am a practicing Zen Buddhist.
Please cite a source for this. Ethics are supposed to help with Buddhist practices towards achieving enlightenment from what I’ve read, not the other way round. If they came about as a result of meditation automatically, the Vinaya would not need to list so many rules for monks and nuns.
Neither meditation is said to be sufficient for enlightenment, at least to Buddhists who are not Zen (or Ch'an) practitioners.
We cannot just ask Siddhartha Gautama anymore about the practices and his words were mysticized and changed over generations, as were ethical rules and especially the added monastic rules.
Even Pali Canon is suspect in pieces and that's a more reliable source in the practices he reformed.