Lagartha interest in the Christian, which I admit may be the creator push, but it make sense in that she knows he could not really be loyal to Ivar and if he can fight, then he could help because there is another war of this kind coming and they just lost allot, and if he won' be loyal then kill him then you could kill him then.
More importantly though Lagartha is starting to turn into Ragnar a little in that she is tried. Season 3-5 Ragnar. Volience and competition is interesting to watch from a far, in fun to watch. When you win, for a while it can be fun to be part of it, of course its never fun to lose.
But when you have won time and time again, and achieve just and out everything you wanted, volience just become tiresome, and holding on to power is a tireless burden. Especially when the things you care about have changed or you no longer care about them.
Lagertha greatest drive in season one was the same as very viking, raiding and plunder, she did that, when Ragnar cheated, her drive change to bitterness and self depency. Finally, it was revenge and reclaiming her queenship.
Now, that all those things are past, she just want to hold on to what she has and go back to her first love (family and raiding), however, since there is no peace around her to chase her first love, she must begin to question the first premises: that is, the whole viking way: the only thing that matters are the gods, family and raiding.
Why would she questions these, well, because if you have everything you want and are not happy or at peace, then you must questions the first assumptions because they got you here.
Just like the vikings have always been a physical torn in the side of the Christian world. The Christian world view has always been a spiritual torn in the minds of vikings.
Now I once heard a quote that a great empire cannot fall unless there is inner conflict. This is the same with a belief system. When a viking is determined and sure, like floki, season one, the only thing he has for both the Christian and his world view is a sword.
Lagartha is however no very confident in her inner confidence although she is very confident in her battle skill and planning. Three quotes from this season: "I have learn that you never know what a person will do" "I am tried of betrayal" " a real believer, like you?" I think she is ready to listen to what a Christian has to say, although she is not a fool and won't hesitate to kill him, but will hold on to her beliefs as tightly as possible
