Here's a question. The real answer is "because they need a reason for Jesse to be kept alive." And that's fine, whatever.
But, really, if you just got 70 million dollars dropped in your lap why would you need to continue on with the highly illegal, high rate of getting busted and spending the rest of your life in prison act of cooking meth? Especially since Uncle Hitler was just mocking the others for being greedy. Dude, you got 70 million dollars! You make, what, from each cook? Half a million maybe? There's so many ways to get busted cooking and transporting meth that I just don't see why its worth the risk at this point.
I'd be a little afraid of Lydia and her overseas buyers. Not that they seem afraid of much, but they are just one part of the huge distribution line with some dangerous people on all fronts.
Todd just wants to impress Lydia so that he can get her in the sack. The Aryans obviously didn't care about making meth anymore, since they weren't trying to get Walt to cook and were willing to kill the only other person who could cook as well (Jesse). Todd is doing this to get Lydia.
Walt is a villain now.
The thing is, Walt has always been a villain. Heisenberg is his true self; he only played the part of a good guy.
Perhaps Heisenberg is all of our true selves, if history is any judge. Perhaps that is the point that Vince Gilligan is trying to make.