Shobit Revenge- Why?

What is reason for Shobit Revenge? OK, His love has died, but his Mum asked him but he didn't say, was happy to marry Gunjan for Brothers happiness etc.

Intinaly, Revenge was understandable, as He thought Nandani made plan of Getting Gunjan here etc, but this has since come out that Gunjan Grandma made it with Rijvi