I try to remember if comic book artist Don Rosa used to be an architect or a civil engineer. Anyway, I have a collection with all his Life and Times of Scrooge McDuck comics that includes a lot of comments about how he made them. And he keeps mentioning how much he used the skills he learned for technical drawings in his other career for his comics. So there's an inspiring example.
It depends on what you want to do of course, but going from architect to illustrator seems rather logical to me. Me, I'm educated as a language consultant while also working as an illustrator. It's a weird mix, but even there I've found ways to strengthen one career using the skills from the other.