In the mid-'90s a Ford Motor vice president explained the rationale for the Mercury brand.
"It's just so we can fill all the Ford plants," he said over lunch. The point of Mercury was to sell a few extra units after the real Ford brand had completed its sell.
So if Ford had a plant that built 250,000 cars a year and Ford Division could be counted on for 210,000, Mercury could sell the scraps.
It was then -- and is now -- a horrendous way to grow a brand that buyers will actually care about.