Brunelleschi was working at the height of the Renaissance, in the early 1400s. They weren't short of book learning in renaissance Florence, but that's why it's

Brunelleschi was working at the height of the Renaissance, in the early 1400s. They weren't short of book learning in renaissance Florence, but that's why it's called the renaissance. I imagine medieval cathedral building, e.g. Notre Dame starting more than 200 years previously, might have looked very different. They couldn't build a dome like Brunelleschi back then.