The human councilor choice makes no sense

You get to choose whether Anderson or Udina joins the Council, and if you pick Anderson, he’s still on it two years later, but then six months later Udina’s replaced him. Why? Why would Anderson leave after two years and destroy all his political contacts? Did the Council kick him out? Did he decide to go back to Earth? Is it so he can focus on fighting the Reapers? Is just for writer convenience? Basically, you make a choice and it turns out to be for naught. (It’s not like the Council listens to Shepard about the Reapers either way.) The only way the start of ME3 makes sense is if you pick Udina at the end of the first game.

Edit: Apparently everything is explained in the books. I had no idea Kahlee Sanders was such a huge character.