Is there really a difference? I feel like if you don’t know something, that kind of makes you stupid, right? If you don’t know historical facts or mathematics—at least the harder stuff, like algebra or calculus—or if you don’t know about advanced political topics, then you’re kind of a stupid person, not just ‘ignorant.’
Ignorance is simply the absense of knowledge. A newborn baby, for example, is ignorant of pretty much everything in the world.
Stupidity is knowing something is wrong and doing it/saying it anyway.