The Gemara mentions a story of two deaf men that would come to Beis Medrash. At one point they got their hearing back and showed themselves to be very learned. So we see that there was an awareness of the possibility of a Cheresh being as smart and learned as anyone else.
As for the Shotte, I can’t see why it should be any different. Depression was never a sign of a Shotte. Acting foolish ans senseless was the point.
I once heard a story of boy who had no social understanding whatsoever. His father sent him to a tutor to train him to be normal. He came home perfectly normal and so his father figured it’s time to marry him off. As they were sitting by his Tena’im, people came by to shake his hand. In front of him was a pitcher, with its side facing the young man. As everyone stuck out their hand to him, he put his hand through the handle of the pitcher, being the shortest route, and shook their hand. The father was aghast. He turned to the tutor and asked him, “is this what I’ve been paying for!?” The tutor answers, “How should I have thought of the possibility of a pitcher being in front of him, at his Tena’im, in the perfect angle?”
The point is there is only a certain amount you can teach.