The carrier deal was also a surprise to them, but if you believe this anonymous former RIM engineer they also didn't think it was possible to do what the iPhone did and still have acceptable battery life:
"RIM was even in denial the day after the iPhone was announced with all hands meets claiming all manner of weird things about iPhone: it couldn't do what they were demonstrating without an insanely power hungry processor, it must have terrible battery life, etc. Imagine their surprise when they disassembled an iPhone for the first time and found that the phone was battery with a tiny logic board strapped to it. It was ridiculous, it was brilliant."
A little context here might be good. The supposed disbelief of Blackberry was their carrier deal, as they themselves were not _allowed_ to sell phones with that feature set.
It wasn't unthinkable to build it engineering-wise. (It was expensive yet with underwhelming features, a 2G phone with no apps at a time when even feature phones had 3G and apps for almost five years.) It was unthinkable business-wise. Those rules are easier to play hard and fast with.
That there is unfounded criticism doesn't mean all criticisms is unfounded.