He was homeschooled but he still needed to learn the school curriculum. Stop making excuses.
Hikaru was homeschooled so that he could focus on chess and compete extensively, without school getting in the way. I'm sure he fulfilled his minimum academic requirements, but obviously chess was the main focus in his life.
The same could be said of Caruana, who was also homeschooled for similar reasons. A childhood built around chess to the exclusion of most everything else - it's not much of a surprise that Caruana became a powerful player, as well.
I'm not sure what excuses you think I'm making, though. I'm merely offering a plausible explanation for Hikaru's chess skill that doesn't require an astronomically high IQ.
more ike 1 iq