You'd think that close ties between tech-wonks' two favorite companies--Apple and Google--would be a dream come true. But pressure on Google CEO Eric Schmidt to resign from Apple's board of directors grew so strong in recent weeks that news of his departure today prompted only satisfied grunts. Instead of asking, "Why did this happen," many asked, "Why didn't this happen sooner?"

As Michael Hickins of BNet put it:

There is no question that Schmidt should have done this months ago, when Google's plans for an operating system that would compete with Apple's Safari became settled. Apple's statement only serves to beg the question of why he didn't step down earlier.

Still, the explanations for his departure don't exactly line up. Some believe that the two companies were headed toward a competitive collision, while others think that ditching Schmidt was a more cynical play to short-circuit government investigations. Below, the five strongest theories so far:

• iPhone Conflicts Broke the Alliance, says Erick Schonfeld at TechCrunch, "Google brought down the disapproving scrutiny of the FCC onto Apple on Friday night, and on Monday morning Schmidt resigned. It is difficult not to make a connection between these two events."
• Jobs Booted Him Out, says Om Malik at GigaOm. "The way I see it, Apple should take these hostilities one step further: Kick out Google Maps from the core of its service and replace it with Yahoo Maps. And as for search, there is this thing called Bing."
• Only Fear of the FCC Stopped Them says Erik Sherman at BNet. "How about, "We decided to see how long we could get away with it?'"
• Their Corporate Cultures Were Incompatible, says Michael Hickins at BNet. "The two companies may well continue to admire each other, but as rivals and from a distance that's only growing colder."
• Google Was Ready for a Mobile War, says Larry Dignan at ZDNet. "It's Android vs. the iPhone and the games are just about to begin."

Was there no one who thought Schmidt should have stayed?

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