Before we go ahead, we would like to point a few things out. Nitish and Lalu are in an alliance with Congress. Kejriwal is showing his support for Nitish Kumar, directly AND indirectly. Hence, obviously, Kejriwal is supporting Lalu against BJP in Bihar just so that he may weaken BJP enough to make inroads in 2019 elections. This is what is the truth no matter what AAPistanis think on the matter.
Let us see how things have changed between 2013 and 2015. How Lalu went from someone AAP would not even like commenting on to a person whom Kejriwal would prefer to see in power rather than BJP. See how Kejriwal became a sane politician for Lalu instead of a hypocrite who will be worst person in Indian politics (his words, not mine).
So, here is the video for you to have a look at.