It's not really about needing to change Maemo. Clearly Nokia already felt it was a good product and was planning to continue developing it. No doubt about it, Nokia's been surprised and happy with the response to the N900 and Maemo. But they also realized promoting Maemo by themselves even with a massive and expensive ad campaign probably wasn't going to be enough for Maemo to get where it needed to be in terms of market share and developer interest.

For long-term survival in the smartphone/pocket computer marketplace against Apple, RIM and Android, it was becoming obvious that it would take strength in numbers - really big numbers. Maemo/MeeGo would have a much better chance of survival - even eventual dominance - if not one company (even one as huge as Nokia) but many companies used, supported and promoted Maemo/MeeGo. So they smartly teamed up with another absolute monster in Intel to add clout, resources and respectibility. And open-sourced MeeGo to add further incentive for other companies to get on board. And it's working, if news of support for MeeGo from a long list of companies like EA games is to be believed.

The support of an OS by many companies against one is how Microsoft overtook Apple's early lead in PCs and how Android will likely soon overtake the iPhone's early lead. Like Apple with PCs, Sony tried to rule VCRs with the BetaMax system allowed on only their hardware. but were overtaken by the VHS system supported by many manufacturers. Nokia and Intel aren't ignorant of that kind of history. They can see that history proves that eventually open (or even semi-open) systems will break the stranglehold of totally closed ones. Monopolies never last forever.

IMHO MeeGo has a solid plan that if properly executed could make MeeGo huge in 2-3 years.