Please help me understand the last sentence of this paragraph

"That J.M.W. Turner, an outstanding and innovative landscapist of the early nineteenth century, held the position of Professor of Perspective at the Royal Academy indicates the durability of the hold which renaissance theory maintained over early modern painting. It was only the challenge by various of the ‘modern’ movements in our own time, particularly Cubism, which stressed the relative nature of vision as revealed by the camera and of space as theorised in physics which fully and effectively disposed of the dominance of perspective as the central convention for realist representation of nature."
I couldn't figure out what the "it" refers to. Does it refer to the long part--(what brought) by various of the ‘modern’ movements in our own time, particularly Cubism, which stressed the relative nature of vision as revealed by the camera and of space as theorised in physics which fully and effectively disposed of the dominance of perspective as the central convention for realist representation of nature. Thanks!