He understood that indeed, in just a small timeframe, just as well as he understood how they don't live up to her image of a great loving family at all. He saw them for what they are instantly, which is why seeing her love and care for them made him feel it was a hopeless situation, that she was best moving on from that undeserving lot. Heck even he couldn't accept the fact that they'd throw her out of the house based on his lies and that it was purely a one-sided 'relationship'.
He had sensed out the family's mistrust way before, though, or he wouldn't have chosen to do that tamasha for revenge. He did it bcz he expected them to believe him and not her. No normal family would hear that kind of crap about their daughter from a stranger and believe it — no matter how many "proofs" were presented. He had known beforehand that Pallu's footing wasn't strong enough in that family (probably from the time VD had come to visit him), even though she basically lived her life for them. He knew they would act out against her, he expected it. Yet to see it actually happen, to witness firsthand the kind of nothingness they feel for her — that's getting to him. Especially now that he actually cares about her and is seeing things from her side.