He noticed the hot dance.
He saw the interaction between Arnav and Khushi afterwards.
He noticed the sweet moment when Arnav indicated that her earrings were missing.
He noticed how she smiled at him from the Podium after receiving the NatrajâŚ.
Do you think Shyam will be the first to sense ARHI love and then create havoc on their lives?
If you remember the Wiki article it said Shyam turns nagative after he finds out Khushi loves Arnav. Though he is already nagative now he hasn't harmed Khushi. Maybe now he will try to harm her knowing that she will never willingly be his (now he has the delusion she does not want him because he is married)