Nokia could absolutely not afford to release Maemo 5 late. With Symbian ^3 and ^4 far ahead yet, they needed something this year to keep their "street credibility" as being a top player, and that was the N900. Their stock even went up when it was released!

It is sad that people confuse pretty UI with advanced capabilities, but such is the state of things, and the only device with a top notch UI was the N900. Consider also how much time had passed since the N810 release, that there was no Elephantia version of the OS after Diablo (Elephantia features got integrated into Fremantle); this forum itself was becoming a wasteland before the announcement, and people were screaming bloody murder after the delay...

Yeah, they couldn't release it later.