My assumption has been that the author was pressured to add a backdoor or abandon the project since it was an issue for law enforcement. After TrueCrypt stopped releasing new versions, it was audited and there was no sign of any backdoor or flaw in the encryption. Now on device encryption is more common but so are cloud backups, and law enforcement has found that going after cloud backups is much easier to subpoena. Plus there is a more mature industry for law enforcement to provide tools tools to bypass encryption without the developer complying.