Saying that Democrats killed the 2005 bill "while Mr. Obama was notably silent" oversimplifies things considerably. The bill made it out of committee in the Senate but was never brought up for consideration. At that time, Republicans had a majority in the Senate and controlled the agenda. Democrats never got the chance to vote against it or to mount a filibuster to block it.
By the time McCain signed on to the legislation, it was too late to prevent the crisis anyway. McCain added his name on May 25, 2006, when the housing bubble had already nearly peaked. Standard & Poor’s
Case-Schiller Home Price Index, which measures residential housing prices in 20 metropolitan regions and then constructs a composite index for the entire United States, shows that housing prices began falling in July 2006, barely two months later.