Do we really need a deep conspiracy theory angle to explain the deprecation of a horribly lagging OS (Symbian) and a next-gen OS whose development was severely lagging even behind WP7? The board brought on Elop to do precisely what he did - any ire should be directed squarely at them. Say what you will about RIMM, at least they aren't striking at the prospect of QNX replacing their OS.
The partnership is still suspicious; any reasonable person would tell you Nokia should have picked Android instead. There's no competitive advantage picking up WP7, unless microsoft wanted to subsidize every nokia handset
I wouldn't discard that possibility. Phone makers have to pay to call their Android sets Android and to have the Gmail, Google Maps and other Google properties on their phones. Maybe Microsoft is giving them a boatload of money and saying "spend this money to make WP7 suck less, for we can't to it ourselves" on the condition they sell only WP7 phones.
We don't know what's in the package. This could give Nokia time enough so it can be carved into smaller sellable pieces before the whole thing collapses.
The whole thing would collapse anyway without an aggressive course correction. MeeGo isn't going anywhere and Symbian is doomed. They could have gone Android, but I guess the board thinks the company is doomed no matter what is done and that WP7 is what brings it more time.