Sandy,
I think you want something looking like the plot here, right?
Drawing a surface (p1 in your case) needs 2 axes (x and y), yet plot1 is 1D. Even when plot1 is drawn as lego there is only one axis (x; of course, ignoring the height, z); the “depth” is not a binned axis, but just an effect to make it look 3D, so where/how would the “y” bins be shown?
Instead, maybe you can copy plot1 into another 2D histogram, but using only one y bin, e.g. use y=0 for all x bins; then probably you can draw what you want.