Well, if we are going to speculate, I'll offer a guess: the crowd funded security audit made the developers lose their enthusiasm.

I believe I read in another thread that TrueCrypt did not get many donations. I'd be a bit depressed if I worked long and hard on a project that people seemed to appreciate, but not enough to crack open their wallets and toss a few bucks my way, and then some third party comes along and quickly raises $70k to audit my code.