Mangala Exp was direct decedent of 131/132 NZM-MAQ/Cochin Janata Exp & has never been part of big 3 (Kerala been KK) until Kerala got split from KK & Kerala Mangala Exp commenced by Janta Rake augmented with Kerala, creating big 4!!
Kerala Mangala whisked as Kerala & Mangala quite soon.!! Janta was upgraded as Kerala, but folk recalls it as an upgrade with no trace of big 4, which it was!!