In response to your first question, I've heard it said that "a," if not "the" root cause the Great Depression of the 1930s was usury. That strong anti-usury laws were put in place in the aftermath of that economic collapse. That sustained economic growth was obtained, a middle class was created, until the late 1970s/early 1980s. That's when the anti-usury laws were slowly but systematically removed. This set the stage for the S&L crisis in the late 1980s and the other economic malaise since then. So yes, the government is at fault if we want to be completely cynical about it - because Congress removed the prohibitions on usury, thereby enabling Wall Street to do to itself what it had already done once before.
As for the second question, SA's first paragraph sums it up nicely.
Percy