Well, in fact Giotto was appointed architect for the Campanile some years before his death just because of his established fame. His fresco's were revolutionary as they introduced emotions and finally stepped completely away from the hieratic byzantine tradition to a full naturalistic art. Some say the 'Rinascimento' started with him. Vasari researched Giotto because he wanted a historical foundation for his beloved Firenze. The fact that he glorified Giotto & his alleged teacher Cimabue as forerunners in his Vite, fixated their important position in art history without a doubt!