This is due to primarily to advances in technology (more reliable ovens, manufacture/availability of food molds) and ingredient availability (refined sugar). When removed the icing cooled quickly to form a hard, glossy [ice-like] covering.
At that time cake hoops--round molds for shaping cakes that were placed on flat baking trays--were popular. Many cakes made at this time still contained dried fruits (raisins, currants, citrons).
Since the Second World War, however, usage of the term has honed in on an elaborate 'cream cake': the cake element, generally a fairly unremarkable sponge, is in most cases simply an excuse for lavish layers of cream, and baroque cream and fruit ornamentation...
The word gateau is the modern French descendant of Old French guastel, 'fine bread'; which is probably of Germanic origin.
Most were probably rather sickly, made from cheap sponge filled with 'buttercream'..coated with fondant icing. French gateau are richer than the products of British bakers. These products naturally relaxed into rounded shapes.
They involve thin layers of sponge, usually genoise, or meringue; some are based on choux pastry. The later are rarely dairy cream; instead creme patissiere (confectioner's custard--milk, sugar, egg yolks, and a little flour) or creme au buerre (a rich concoction of egg yolks creamed with sugar syrup and softened butter) are used. By the 17th century, cake hoops (fashioned from metal or wood) were placed on flat pans to effect the shape.
In its northeastern Old French dialect from wasel it as borrowed into English in the thirteenth century, where it survived until the seventeenth century." ---An A to Z of Food and Drink, John Ayto [Oxford University Press: Oxford] 2002 (p.
138) "The word 'gateau' crossed the Channel to England in the early 19th century...
Hearth cakes are still made in Normandy, Picardy, Poitou and in some provinces in the south of France.Casse-museau is a hard dry pastry still made today'...petits choux and gateaux feuilletes are mentioned in a charter by Robert, Bishop of Amiens in 1311." ---Larousse Gastronomique, completely revised and updated [Clarkson Potter: New York] 2001 (p. The original dividing line between cake and bread was fairly thin: Roman times eggs and butter were often added to basic bread dough to give a consistency we would recognize as cakelike, and this was frequently sweetened with honey.