Lightning hitting a Villager entity will turn it into a Witch, which is desired behavior.

However, in the unlikely event of two or more lightning bolts hitting one Villager, two or more Witches will be created.

The number of lightning bolts and spawned Witches is correlated.

I’m posting this to get info if this is a bug (pigs and creepers do not mulitply under the same condition) or intended behavior.