"Andrea (Pisano) was working at a time when the Roman Catholic Church wanted to make its lessons visually accessible and relatable. A century before, St. Francis—preaching poverty, a love of nature, and a compassionate Christianity that emphasized the value of the individual—had brought a new humanity to its teachings. At the time, the dominant Byzantine painting style was abstract and emotionally distant, with starched, flat figures in frontal poses standing in front of gold backgrounds symbolizing divine light. This was reflected in Bonanno’s doors, whose stiff figures, without facial or corporeal expression, still belonged to that Byzantine paradigm. In addition, the reliefs lacked any sense of spatial depth.
Andrea looked away from that tradition and toward the frescoes in the nearby Church of Santa Croce..." Read the article here (paywall may apply.)