Ignorance is not having the specific knowledge requested, so being ignorant is NOT an insult if you never had the knowledge
Stupid is not being able to apply the knowledge you do have
An intellectual has knowledge in specific areas, and they are usually STUPID, because they can not apply that knowledge outside its framework
Smart is not book learning, never has been, smart is being able to apply the knowledge you have to solve new problems in new situations, and then learn from that to apply it to the next new thing
"Think outside the BOX" is often used, the BOX is what you already know, an intellectual is trapped inside their BOX
A smart person can take whats inside their BOX and apply it to something new that's outside their BOX, making their BOX bigger