Though he is advised by Vidura, he follows the instructions of his son and it was at the instigation of Shakuni that he challenged the son of Kunti.
विदुरेणानुनीतोऽपि पुत्रमेवानुवर्तते। शकुनिर्बुद्धिपूर्वं हि कुन्तीपुत्रं समाह्वयत्॥