More to the point, it also used space more economically by having the gun in the front hull as opposed to separate superstructure. That makes for less frontal surface area ergo thick “main belt” glacis plate which, obviously, saves weight, as did leaving the sides very thin.

Still by no means a small or light vehicle though; Chars-Francais gives ~60 tons, 2.7m height (presumably including the cupolas) and 3.1m width. (Lenght is listed as 9.5m, but since that obviously includes the barrel it’s not terribly useful.)
It merely wasn’t as huge as the massive steel bricks the Germans liked to draw up in the final years; the in-game weights of the E-50s already, presumably at least in the right ballpark, are already 60+ tons…

Anyways, just thought I’d point out the comparision didn’t seem entirely valid.

Sources:
“Special Panzer Variants” by Spielberger
“Waffen und Geheimwaffen des deutschen Heeres 1933-1945″ by Fritz Hahn

Both were military engineers in WWII Germany.