If Obama was bound to do that good (considering as you keep pointing out that he won 52.87% of the popular vote IRL) without a financial crisis why the hell would he do only .2% better if there was one?
A last minute gaffe by an opponent might give one .2% more of the popular vote come election date. A financial crisis that happened a month before election? A bit more I think.
For the record I see Obama winning around 50.8-51.2% of the vote without a crisis.This site says 52.87%; other records show it was 52.92%.
Obama polled at least five points better than McCain early in the election season. That would be just a 7.46% shift. 2000 Bush had a 8.00% shift (of Bob Dole's 8.52% loss). Ronald Reagan shifted about 11.80%. Obama was going to win 2008 regardless of the meltdown. And he was going to win it by at least 7 points.
