He did take the sankalp and was about to close the mandhir door, even after Radh said about the Mandhir and its belief... ...he opted out for the truth.
there was this sign from Kahna( the shank sound and the govinda gopala, which means good signs) So it made his sankalp more strong.
So do u think his sankalp will go in vein just like that, his decision while making the sankalp was not easy. He also had to go though tough phase while making it.
So do u think he'll just let it go and bend tomorrow in front of the society?... ... will he loose his own trust on his dharam and will he support the false?
edit:
and also the words of Padma which he over hears, Padma was talking about Radh, he becomes emotional and wanted to say something...
even the words of Padma didnt let him waver in his decision.