Okay, so, this theory isn't very complicated, just a bit weird until you actually understand why I'm making this. Just hang on, and you'll get what this all means.
Necromancy is the magic of raising dead creatures, or just organic matter from the dead. In the case of Minecraft, necromancy has been around since the early days. Not necessarily actually raising people from the dead, but the people that were most probably raised from the dead were always there in the form of zombies, skeletons, and later husks, and strays.
Later, with the release of dungeons and the book: The Rise of the Arch Illager, we found out who actually made these zombies and skeletons in the first place. We can say pretty certainly that the inhabitants of the Nameless Kingdom were the ones that created the undead.
So, last night, I was just thinking about how there were zombie villagers, but no zombie illagers. I came up with the most logical solution, which is that illagers are immune to necromancy for some reason. And then something popped into my mind: it must be totems of undying.
This discovery might actually be more important that you think, since this can explain a lot about the relationships illagers have with the undead in vanilla Minecraft.
Let me explain. The fact that totems of undying were there before dungeons could mean that before RotAI, the illagers were already "befriended" with the undead.
Two of the most logical reasons are listed below.
- The Nameless People were envious of the illagers having a way to get by death without the downsides necromancy might have
- The Nameless People helped the illagers with the creation of Totems
Take this as serious as you want, but just know, the relationship between illagers and undead might track back longer than you think.