The amount of money that was flying around the debt markets in Sep/Oct 2008 dwarfed any single bank’s or fund’s size.
To take down the money market funds in the US, we’re talking of moving hundreds of billions of dollars in a few hours. The Fed went into full panic when they saw in excess of $550 billion move out of money market funds in two hours.
Soros is rich, but he isn’t that rich, and he can’t affect that much money in such a coordinated fashion. The money flows can be easily explained in the height of a panic among “professional” money managers who saw all of their assumptions about how markets worked being broken in quick succession.