so they couldn't make up their minds in the case of the tri star, L1011 and DC10 eh?????????????
......and the Trident and 727....... All of the tri-jets were designed and built in a time where more is better - fuel costs were less important - the industry was fat with cashflow and image was everything.
A large 2-engined airliner was unthinkable back then - not only due to the prevailing beliefs of the designers and the engines that were available to them - it was also the collective public memory of the not-so distant piston powered days would make a transoceanic twin a most unattractive conveyance for an airline to sell to passengers at that time.