Not hard to figure out why: increasing questions about the Clinton Foundation--it seems the MSM realizes the charges from
Clinton Cash can be verified!--could make the Clintons vulnerable to a
foreign legal investigation, particularly banking authorities in places like Switzerland and Singapore with their large banking centers. After all, the "donors" have to deposit the money somewhere outside the USA before it gets transferred to the Foundation.
In fact, I think the increasing scrutiny of the Foundation could start to unnerve Wall Street, because for many Wall Street firms, the LAST thing they want is another major legal investigation of its financial operations.
All good points. Hillary's increasing negatives, as well as continued questions about her health (fueled by her conspicuous absence from the campaign trail) are a growing problem for her. But the other factor is that Trump has pivoted and has been talking more about his vision for the restoration of America while all Hillary and her surrogates have done is continue with their tired and increasingly shrill attacks on Trump.
His outreach to blacks, Hispanics, and other groups that the democrats feel they "own" is starting to work. People want to believe in the future, not just hear the usual "my opponent is scum" empty rhetoric.