I don't think it was for the technical fit or performance reasons, but more a philosophy about everything starts with data, and graphics are just visualizations

I don't think it was for the technical fit or performance reasons, but more a philosophy about everything starts with data, and graphics are just visualizations anchored to the data points (or a functionally derived property of the data points). That also means the d3-* libraries compose really well, since the data is the common binding, and not some conceptual class or custom element.