It started in the mid-1960s. The dealers charged with moving metal for lesser divisions of the Big Three started clamoring for more luxurious versions of their largest cars. Rumor has it that the reason stemmed from the division managers being forced to drive cars from the actual divisions they managed, rather than being permitted to choose Cadillacs or Lincolns for personal use. How true this is, we may never know.
This is a companion discussion topic for the original entry at https://www.hagerty.com/articles-videos/articles/2019/06/14/ford-ltd-landau-working-mans-luxury-car