Microsoft is pretty much one of the only companies that could acquire AMD and turn it around. Much how people complained of nvidia gameworks giving it a unfair advantage against AMD, microsoft has the ability to develop in house features only ATI/AMD hardware could take advantage of initially and give nvidia/intel a real run for their money

It definitely helps that microsoft could likely get a significant discount on the purchase price as well since amd is seen as dieing. The arrangement between intel and MS is very old and involves significant cash flowing both ways. I imagine as microsoft has more internal pressure to show more profits that this line of thinking was bound to come up