I'm not a big believer of any collusion theories (see links below) but I feel that JPM, BAC, C, WFC, etc all were all on life support but able to sustain a heart beat for just a few more days than WaMu until TARP saved Wall Street.
I think the seizure was done out of fear b/c of WaMu's reputation as the king of the subprime lending practices on the street whether or not they really were it didn't matter. Remember, on Wall Street perception is reality. As stated earlier, mark-to-market accounting was a serious gash to their jugular and I feel that the lack of liquidity b/c of panic/fear on the street is what led the fdic to prematurely seize coupled with bear raids on their credit default swaps.
Here's some interesting articles that I've read about their CDS costs that haven't been talked about too much on this board. It would be interesting to see if JPM (or any other investment bank) was bidding up WAMU's CDS's out of speculation and not as a true hedge.
Sept 10th CDS prices looking at 80% chance of default http://slog.thestranger.com/2008/09/credit_default_swaps_indicate_theres_an "Washington Mutual Inc., the largest U.S. savings & loan, failed to interest suitors in a purchase this year because new accounting rules for devalued loans are driving away buyers, two bankers involved in the talks said."