You also have to remember, if AMD goes under, companies like Intel and Nvidia would likely be considered monopolies, and would therefore be broken up by the government into 2 or 3 smaller companies each. So Intel and Nvidia need AMD to keep themselves alive as well, just like how Microsoft needed Apple.
More Info on Monopolies:
http://www.investopedia.com/terms/m/monopoly.asp
And like Karadjgne said, healthy competition is needed for advancement and progress, AMD has fallen behind in CPU power, which has made Intel kinda lax, just look at the performance differences between Skylake and Haswell, or should I say, lack of performance differences