TT: that's one view of causes for DC-10/MD-11 outselling L1011...but:
the root issue was splitting the market by launching both, EA+DL L1011-1, AA/UA DC-10-10. Both programs lost megabucks, contributing to Lockheed's exit from Commercial, and to MDC's absorption by Boeing. Just contemplate the chaos if Lockheed had announced a civil variant to follow very quickly after C-5 In-Service Date. That dribble of 747 deliveries after first rush would have been a drought, maybe devastating Boeing.
Engine out ex-Denver was the 1967 reason for trijet, and that became insignificant as big fans became so reliable. Every other operator was happy with 2 or with 4 engines.
2 very political impositions of Pratt as DC-10/40 did not make wider impact, nor were the cargo conversion aftermarket programs crucial at the point of initial selection for pax operation. British-contract-designer-influenced, L-1011 was heavier, so its apparent operating economics inferior to DC-10.