Apparently French President Nicolas Sarkozy threatened to pull France off of the euro, which helped push the 750 billion euro intervention through. But, Ex-SKF provides some numbers that support the theory that Sarkozy was most certainly bluffing (recreated below in chart form).
Merkel probably relented because she didn't want to be accused of breaking up the eurozone and endangering the EU collapse. She should know better, as France cannot possibly afford to go it alone. She should have called Sarkozy's bluff.Source: NY Times