Actually, it is always bad management
Or they wouldn't have become a well-known and loved brand to begin with.
A lot of it has to do with the shift from earning a profit through value addition to making money with the capital markets, tax breaks and other financial instruments.
Soon, many companies only saw their "products" as secondary.
Then you add in the stupid management fads, like mentioned above. Did BMW really need to buy Rover?
Did Daimler really need to buy Chrysler?
Both decisions were exactly like wanting to have cancer so you can have lots more "cells" in your body.
I'm not talking here about the time honored practice of buying your competition to slit their throat. Whirlpool has probably done us all a favor by putting Maytag out of our misery. Did we really need any more Amanananantags or sucking Hoovers?
And after all the horrors done in the name of "traditional brand names" (Amananantags, Hoovers, Duals, AEGs, etc.) maybe it is better to die a noble death than to be used to hype shit dressed up as shinola).
In the end though, after all the mergers and acquisitions, one thing remains: The Chinese. They have the patience, they focus on value addition and, don't fool yourself, the quality and the creativity (I teach young Chinese engineers; they come here to learn, they go back home after turning down jobs at Siemens and BMW)and long term orientation make them your (and our, though our quality will buy us a little time) worst danger.
Oh, well, I can see the boys building that boat for me out in the harbor now. Don't forget the lashings and tinder so it'll burn brightly...