as someone who can remember what it was like when the first Mustang was introduced in Spring of '64: what a difference!
as I recall, they knew they'd sell well, but were surprised at the demand......but they reacted quickly, switching over additional plants to meet the demand.....and setting all those sales records.
now.....they knew the old 'Stang was still selling over 150,000 a year....and had to have some idea of what the demand would be for the new style.
so they relegate assembly to 1 plant (the Ford/Mazda Auto Alliance facility) with a limited capacity........now running about 4400 a week. if they could make more, they could sell more......but apparently they'd rather sell fewer at a higher mark-up....and lower overhead by closing plants that could be used to make popular models.
Meanwhile, Mazda6 production has to be limited to make 'Stangs.........but they gleefully produce near-identical Fusions-Milans-Zephyrs in a Mexican plant so they can pay lower wages with fewer benies. (and this the company that chided GM for "cookie cutter" cars).
Total FoMoCo North American car/truck production is off about 200,000 units so far this year........that they could make-up by producing more 'Stangs.....but they'd rather bust the union's balls by crying wolf and moving production out of the US.....sad.
Chrysler doing the same thing: US made Neon sedans were still hot sellers (despite no promotion) but discontinued. The PT Cruiser (a Neon plaform with another body) still going great guns....produced in Mexico.