There were a couple guys that went into the J legend. One was the student of Yehushua ben parachia (Sotah 47). He lived about 150-200 years before the Churban. The other IIRC was someone named ben stadia, whom Rabbi Eliezer (who lived through the churban) references around Chagiga 5.
I believe that all the spiritual reasons given for Nittel are just to keep people indoors, so that they won’t get harmed by raving bands of intoxicated Cossacks. Once you attach a spiritual reason, it’s much harder for a layman to think he can decide for himself. Furthermore, the practical reason seems likely because not all Ashkenazim follow it, nor do any Sephardim.