Those who are very aggressive traders have been long and short in the financials for months to the point that the Securities and Exchange Commission put out a list of companies that could not beshorted.
The SEC's removal in 2007 of the uptick rule (which held that a stock couldn't beshorted unless it had gone up in price), as well as its failure to enforce the rule against naked short-selling (an investor is supposed to borrow the shares before he shorts them), increased pressure on beleaguered banks and insurance company equities.
The only drawback appears to be the players getting shorted out of their share of the money considering that the likelihood of injuries in a longer season would increase.
Citron says on its website that its principals may also be trading in the securities that it researches, which means that it likely shorted Evergrande ahead of the release of its report.