Payal wants property- she can now emotionally blackmail Mahi in the name of harming Ria.
Gangu- even though she seems to act indifferent about Satya leaving her, she won't let him go easily, she knows Satya won't leave Mahi, but Mahi will definitely will push Satya away if he keeps trying to prevent her from giving her property to Payal who is hurting her mom.
This benefits both of them, they are creating trouble between SaHi, if Mahi in her emotional state does push Satya away, it will be even easier for Payal to get her property and Gangu can then come in as savior mother for her son.
I think the future episode might be Satya trying to prove Ria is not Mahi's mom and Mahi being emotionally imbalance might not believe Satya and hence SaHi separation.