Just another theory but consider that the TrueCrypt team was always anonymous and considering that their licence is somewhat prohibitive for a open-source proje

Just another theory but consider that the TrueCrypt team was always anonymous and considering that their licence is somewhat prohibitive for a open-source project it's not totally bonkers to assume that some agency or big coorporation developed TrueCrypt in secret and made it public to gain widespread assurance that there are no bugs in the code. Maybe they migrated away from XP and have assurance that Bitlocker is safe for them or switched to something entirely different and have no interest or funding for development it anymore...