Because in ROB it's all about moving on whereas DMG is either circling or moving back!
Because in ROB, the male lead was so in love with his gf but after he got married to another girl he fell for his now wife! Whereas in DMG even after being married for a year Riddhima is shown having feelings for her ex despite of the fact that she is married to a gem of a person like Sid!
Because ROB dint try to re-unite the ex-flames by showing EMA!
Both ROB and DMG was in the radar for closure! ROB survived because they showed the "RIGHT" thing! And it's curtains for DMG because the story made no sense! Riddhima was almost in the verge of confessing her love for Sid and CVs took a complete U-Turn! And is now paying the price for it!!