So, I got this theory or Headcanon/story that the Husks were actually more involved with the Wither, and that the Undead are more unified that we thought.
Like this:
The Husks were Ancient Builders who fled to the Desert, searching for the Stronghold. Along their journey, they lived Nomadically, rarely settling in one place.
Despite their combat-ready nature, their downfall was inevitable — they're running out of food.
Eventually, some of them became desperate, and they practiced one thing that we, as humans, fear — Cannibalism.
They also have evolved from Zombies because of Natural selection.
And have spreaded the Virus/plague even further into the Desert Biome.
And the Undead could've been under the influence of the Wither via the Virus, thus making a new faction: The Undead Faction