When the iPhone 4S was unveiled last week, salivating tech journalists who'd been expecting a drastically different iPhone 5 were unimpressed. But sales of the new phone have been anything but disappointing. The iPhone 4S doesn't hit stores until this Friday, but more than one million phones were pre-ordered last Friday, setting a new pre-sales record. How did the phone go so quickly from disappointment to smash? Here, five theories:

1. It's a big upgrade for 3GS owners
Sure, "the 4S isn't a radical upgrade from the 4," says Harry McCracken at TIME. "But in a country of two-year phone contracts, the most important upgrade market for the iPhone 4S isn't iPhone 4 owners," it's iPhone 3GS users who are due for new phones. And for them, the 4S is a terrific upgrade. 

2. The camera hype is wooing customers
If the new camera — which boasts 8 megapixels and much faster picture-taking — is as stellar as Apple says, then it's truly "a major improvement over the 4's camera," says McCracken. For the hordes who use their camera phones compulsively, there are few upgrades as compelling.

3. The tech press was over-critical
Tech pundits are almost always underwhelmed by Apple keynotes, says McCracken. They were quick to call the iPhone 4S "disappointing," but "pundit reactions just don't map to real-people reactions." The rest of America is clearly stoked about Apple's new toy.

4. Sprint gives Apple a whole new market
The addition of Sprint as a carrier has given a boost to pre-order sales, analyst Jeffrey Fidacaro tells Bloomberg BusinessWeek. Sprint is the nation's third-largest mobile carrier, and it could put the iPhone in the hands of 6 million new users a year.

5. Steve Jobs' death focused all eyes on Apple
The iPhone 4S was announced last Tuesday, and Apple co-founder Steve Jobs died the next day. His passing clearly "pushed the company to the forefront of the world’s collective consciousness," says Andrew Nusca at ZD Net, and may very well have helped boost sales.