“…but in theory, why couldn't it have been possible for GM to keep 50% of the market? “ – Giant Dwarf
Yes, it could have. Ever heard of the Lanchester’s power laws? Frederick W. Lanchester is no stranger to the automotive engineering. But, his foremost contribution to business in general is his theorization of what makes winners and losers in a combat or war. Books about his theory have long been a “must read” for Japanese businessmen (and possibly Korean counterparts, too) and they are following Lanchester’s teaching by the letters.
In mass marketing if you have more than 40% of the market and there are several competitors, you own the market and you can keep that position unless you commit a fatal error, which GM did. If you are a small company faced with the giant, you must localize and specialize your warfare as VW did more than 50 years ago in North America. If you are the giant faced with the localized or specialized challenge, you must crush it with all the might as soon as the challenge appears. Unfortunately, GM ignored the challenges made by VW’s and Toyotas in the small-size, low-cost segment of the market. Arrogance and ignorance are deadly combination.
If the giant knows the game and tries to crush you, then the small guy must move the playing field to someplace else. Eastman Kodak owned the photography film market. Polaroid monopolized the instant photography market. So, Fuji came up with the digital camera. Even though Eastman Kodak originally developed the concept, possibly it did not make it to the market sooner for it could destroy its lucrative film business. While the big guy is thinking that he is the champion of boxing, the small guy must move the ring to the sumo wrestling.