The element that does not square with any theories that suggest benevolent intent behind the change is the recommendation that users switch to Bitlocker. Surely, a Truecrypt developer who got served a gagging order to build in a backdoor would realise that a big and compliant target such as Microsoft would have been subject to the same measure long ago, and likewise that if a pre-existing vulnerability on a sufficient scale to justify this went unnoticed in an open-source project even after a proper audit, the situation is unlikely to look that much better in a closed-source solution (that only the makers and government agencies have access to).

While this might be reading a tad much into it, the language of the announcement, specifically the "...as it may contain unfixed security issues" bit, sounds like what somebody who just came out on the losing end of a heated debate about whether some bug-feature should or should not be considered the former would say. Knowing the vitriol and determination with which software developer arguments are often carried out, this would explain the observed combination of remarkable dedication and haphazard execution.