I have not much to add. There's several well written answers of the subject. Except the side profile in this image was skipped:

I inserted the red lines which show that the projections do nor fit. The side projection is a manually crafted fake which does not present the same 3D item as the upper part. I bet some experienced Illustrator users here have tried to map some artwork on a revolved surface, but failed to get it right and stayed silent of that subject. To stay silent is no wonder because Illustrator's artwork mapping works so inconsistently that it can be difficult to make any difference between wrong settings, program inaccuracy and geometric impossibilities.
Both projections have several manually crafted details. The curves are split and the parts have got non-uniform widths. The side projection is drawn manually to get a pretty shape, but unfortunately the top edge at least belongs to a shape which doesn't have the rotational symmetry. To get more evidence I tried also to project a collection of N x 36 degrees rotated shapes (10 copies of a little distorted ellipse) on a revolved surface:

The left and right edges of my side profile differ radically from the given original. I wouldn't have anything to write about the projection if the original were something like this:

In that case mapping a shape on a revolved surface also would create something worth showing and it would be here before I had written a single line.
Added due a comment which says that my story is valid for an ortographic projection, but there exists also perspective projections which look different.
The commentator (Mentalist) is right. In a perspective projection, where the camera is near enough the 3D item, the dimples at the ends of the top edge could be invisible (behind the horizon).
But the original side view cannot be at the same time a perspective projection and present a rotationally symmetric piece, because there's 2 straight horizontal lines: The bottom edge and the line through the upper edge hilltops. In a perspective image at least one of them should be curved.