Trump calls Warren "Pocahontas" all the time. Why did he get so confused when Biden called him "Abraham Lincoln"?

Trump is too dumb to understand sarcasm.

Biden isn't known for having a detectable sense of humor. He is however known for getting confused and calling his sister his wife. Trump probably thought it was just another Alzheimers moment. 

Biden was confused and thought he was talking to Abraham lincoln

Donald Trump gets easily confused because he is an idiot. Biden's sarcastic jab referring to Trump's usual ridiculous statement about African Americans apparently upset him.  

He wasn't confused at all.  Biden was confused about the actual conversation.  LOL

Actually, Trump took the high road and opted not to pounce on Biden's dementia-driven gaffe.

He didn't get confused. Biden did.
Didn't you see the sheepish smile on Biden's face that
said, "oh uh, I must have messed up again."
Trump said he did more for Blacks than anyone
with the exception of Abraham Lincoln.
He didn't say he WAS Abraham Lincoln.

Trump is a better critical thinker, but possesses less social skills than Biden, and he may even take things literally.
Biden may be more social, but lacks in critical thinking
skills. The two are inversely proportional. 

I'll take the one with the ability to understand how the economy works, and that's Trump. I don't care if he doesn't have great social skills. That means nothing to me. 
Biden will smile and nod at all the right times;
Well maybe not, he has trouble articulating sometimes,
but he is a zero when it comes to understanding how
things work.
The government will not provide sustainable jobs when
it comes to clean energy.
The private sector must first innovate an affordable alternative to fossil fuel that is profitable, then it will take off. 
Biden has it backwards. 

Many foreigners do not understand sarcasm, and all of Trump supporters have closed their minds to anything negative about Trump, if Joe said it at all. Yahoo Answers is now full of trolls and Russian agents, so without specific references to verify, accusations are worthless here now.

He gets confused very easily.

Well for those not paying attention, Trump said earlier that he did a lot for blacks "like Abraham Lincoln".  SloJoe later referenced it and called Trump Abraham Lincoln feeling that Trump had claimed to be honest Abe.  Trump did not.  It was a mistake by SloJoe.  That's all.  Even squaw Liz Warren would certainly have understood that.