Vivaan has been captive for more than 6 years at that time Chakor was in prison and Imli was ruling, so if he was kept to take revenge of someone then it should be from Imli, only Imli's twisted mind will think of using Vivaan against Chakor.
RV is the last person to benefit from keeping Vivaan, he makes his relationship with Imli illegitimate and makes him lose power and status. On the other hand it's possible that when Imli knew that RV is determined to kill Vivaan that she decided to fake his death and keep him somewhere else.
Also the idea of everyone waiting to take revenge from Sukor while leaving Imli to rule over Azaadganj for 4 years is hard to believe. Maybe it works for KN but not for Ragini.
Sai Sir is a phenomenal actor but viewers get hooked for the story, ML track worked with two clowns as villains but KN blackmailing Chakor was a big failure. Again it's ridiculous enough to make one dead person return so making two return is an absolute joke. They had many options and they chose to bring Vivaan back to life and that's enough.