We don't really know what happened and what caused the TrueCrypt developers to shut it down and walk away. However, the fact that truecrypt.org started warning people against using TrueCrypt does not make sense because it was , all of a sudden, not secure, and recommending "migration" from TrueCrypt to "Bitlocker…?!?", which is proprietary disk encryption software, included in Microsoft's Ultimate/Enterprise versions of Windows and is known to have a backdoor and is compromised. Rule# 1: Don't touch anything that comes with Microsoft Windows as these corporate entities are hand in glove with the alphabet agencies.
As I said previously in another post, the recommendation to migrate from TrueCrypt to "Bitlocker…?!?" is so much against the very reason for the creation of TrueCrypt. TrueCrypt was created because nothing else could be trusted. Things just don't add up. There is something very fishy here. What comes to mind right away is the probability that the TrueCrypt developers might have been contacted and bullied by one of the "alphabet agencies" to create a backdoor in the encryption software, to which the TrueCrypt developers simply said "no!" and decided to shut it down the way Lavabit did.
Thankfully, the efforts are already underway at truecrypt.ch to revive and resurrect TrueCrypt.