During WW II vast systems networks were created for oil production, transportation, and refineries, and all were in place operating at full capacity in 1949. And the price for oil remained low, and oil drove the U.S. economy to great heights in all sectors. From 1949 to 1972, U.S. consumption of oil went from 5.8 million barrels/day to 16.4 million. In 1949, coal represented 2/3's of the world's energy, but by 1972, it was oil at 2/3's. World War II had diverted the American economy away from the consumer to the military, but after the war, the consumer was not to be denied.
During the 1950s GM made more cars than its competitors combined. The only thing that could possibly throw a monkey wrench into GM's colossal success was the possibility of labor unrest. During 1945-46 a bitter strike over low wages at GM lasted over 100 days. GM wanted to teach the United Auto Workers (UAW) a lesson, and held firm with only 0.01/hour separating the two sides. Charles Wilson, the CEO of GM, saw the fantastic future in terms of absolutely massive profits, and was also sympathetic to the workers.
GM decided to manufacture big cars since they generated far more profits than smaller cars. Production costs stayed the same no matter the size of the car, so it was a no-brainer for GM to build big cars. GM had waited a long time for this "Market of Abundance", and GM wanted to take full advantage. Therefore, the yearly model change was crucial for GM, in that the goal was to make car owners restless with the cars they owned, and eager to purchase anothe GM vehicle.
Pontiac was for those that felt successful/confident and that wanted something sportier. Oldsmobile was for the white collar manager or bureaucrat, and Buick was for the elite of the professional class (e.g. doctor/lawyer). The Cadillac was for the top executive or owner of a factory. A Cadillac signaled that a person had joined the proprietorial class; a Cadillac cost around $5000 ($49,745 in 2015 dollars), but it held its value, especially if it was traded in after a year or two.
GM, Ford, and Chrysler were forced to opt for less effecient/attractive cars just for the sake of exterior design changes. Among the consequences was that GM didn't extend its initial technological lead versus foreign competitors (e.g. the Volkswagen Beetle). GM fiddled with styles and design details, especially the "fins", which became the most famous-and-visual automobile detail of the era . . . the fins represented zero technological advance in GM's cars. A fin was "visible prestige", nothing more than an illusion of a more powerful car. That approach by GM, Ford, and Chrylser would come back and haunt the Big 3 in the 1970s during the Arab Oil Embargoes of 1973 and 1979. While GM was selling an incredible number of cars in the 1950s, the corporation, without knowing so, was speeding towards "Dynamic Obsolescence".
Dwight D. Eisenhower was the first Republican President in 20 years, and GM was no longer worried about being accused of monopolistic practices with more than 50% of the market share. The attitude of GM's execs was that if the federal government wanted to stop GM, they would have to find a way to stop GM. In 1953, GM had 45% of the industry's market share, and by 1956 it reached 51%, and that wasn't enough for the GM execs, whose goal was actually 75% of the total market of cars sold in the U.S. by 1958.