Speaking to ANI, Prasad said, "Extra involvement in his family and his son - his putra-moh - became the reason of his downfall."
Prasad went on to praise Bihar Chief Minister Nitish Kumar by calling him an "honest" man.
"After Karpoori Thakur, it is Nitish Kumar who doesn't get much involved in these things and works honestly in politics," he said.
The RJD MLA said that senior leaders of the party had even suggested Tejashwi Yadav's resignation, but Lalu and his son were stubborn about it.
"Our party's senior leadership had suggested Tejashwi Yadav's resignation to save the alliance, but Lalu Yadav and Tejashwi Yadav were stubborn. We didn't expect Nitish Kumar to take such a huge step," he said
Bihar saw a major midnight political drama soonafter Nitish Kumar resigned on Wednesday as Bihar Chief Minister to protest against his Deputy and Rashtriya Janata Dal (RJD) Supremo Lalu Yadav's son Tejashwi Yadav's stubbornness to stay in the Cabinet despite being named in an F.I.R. over the corruption charges.
However, Tejashwi put the onus on Nitish and the Bharatiya Janata Party (BJP) for the latest political development in the state.
Tejashwi said that political vendetta against him exposed the Opposition's viciousness.
"I delivered manifold than what was expected of me. My performance perturbed our ally and the BJP. The vendetta against me exposes their viciousness," he tweeted.
The RJD on Thursday morning was forced to cancel its protest march to Raj Bhavan to oppose Kumar's swearing-in ceremony due to the probationary orders.