It’s not like Michelangelo did it without significant training.
“Among them was Domenico Ghirlandaio, a master in fresco painting, perspective, figure drawing and portraiture who had the largest workshop in Florence.[16] In 1488, at the age of 13, Michelangelo was apprenticed to Ghirlandaio.”
-From Wikipedia
It’s not like Michelangelo did it without significant training.
“Among them was Domenico Ghirlandaio, a master in fresco painting, perspective, figure drawing and portraiture who had the largest workshop in Florence.[16] In 1488, at the age of 13, Michelangelo was apprenticed to Ghirlandaio.” -From Wikipedia
He didn’t paint the chapel until 20 years later.