The party also said Lalu compromised his party's interest to save his son Tejashwi Yadav, who was under immense pressure to resign as Deputy Chief Minister of Bihar.
Bihar was witnessing upheaval soon after Nitish Kumar resigned on Wednesday evening and termed his alliance with the RJD as "unnatural".
The political uncertainty ended on Thursday morning when Nitish Kumar and Bharatiya Janata Party (BJP) leader Sushil Modi took oath as Bihar Chief Minister and Deputy Chief Minister respectively.
BJP leader Nitin Naveen said, "Lalu Yadav is in discomfort. Love for his son led to heavy loss for him. Because of his son, he compromised with interests of the party and sacrificed 'mahagathbandhan'."
Meanwhile, BJP state president Nityanand Rai said, "Now, Bihar will go on the path of development. We are very happy with Nitish Kumar's decision."