It wasn't low down fixed rate long term mortgages that destabilized the system, at all, but rather the "creative" short term ARM mortgage deals and the "creative" ways that risk perception was swept aside in a fit of convulsive greed by Wall St.
It was all enabled by the FRB and Bush regulators, natch, in order to further the fortunes of the already rich and fool the electorate into giving them a second term.  The prime rate was almost instantly reduced to the lowest level since 1955-
http://www.moneycafe.com/library/ratecharts/ratecharts1.gif
And then marched right back up again so as to precipitate the crisis while the Bushistas were still in power. Anybody who thinks this was an accident is delusional.
Meanwhile, the SEC allowed Wall St firms to employ outrageous leverage to facilitate the looting, and taxes for the investor class were reduced to new lows. GWB sold the chumps on the Ownership Society, Terrarist Threat!, God, Guns, and Gays to get re-elected.
Today, of course, low rates are employed in an attempt to hold prices high, something that can't last, because housing still isn't selling. Prices in the formerly bubblicious areas will decline even further in order to clear existing inventory and allow for the "growth" required to let the top 1% take 20%+ of all taxable income.
Can't figure it out? That's because we collectively admire and emulate rent seeking psychopaths who are sucking the life out of the economy. Because we buy into the whole  idea that people at the bottom are dragging us down, rather than the people at the top pushing us down. Because denial is still possible, particularly among the Republican base who couldn't think straight if their lives depended on it, just the way their leadership wants it.