The BBS rajdhani was initially made to run via HWH with reversal and like a clone HWH rajdhani, thats the reason why even at present between NDLS-MGS-GMO, it runs just behind HWH rajdhani.
Then it got diverted via TATA to KGP.
And when Adra route was developed as shortest route connecting KGP-GMO, then Nandan Kanan and BBS Rajdhani got diverted via this route.