Josef stands in front of his mom, Rachel. Rashi says, because he could hide her from Esav. Really? He was tall and good looking and maybe, Esav would want him instead? Really?
Why did Esav leave when the flock were too large for both houses?
Did it have something to do with the "bad" behavior of Shimon and Levy?
The answer to the first question is Rachel was expecting a second son and she had no idea it would be a wolf, and even if she wasn't expecting him, she was still more important than Josef since she could say Add me one that is MORE than the first, and we are talking about the closest call to the Tzaddik Isod Olam. (just so you get a inkling of what Rachel is).
The answer to the second question is when you consider the Esavite neighbors like Hamor and Schem that would lame their whole town to have more females for themselves and a new exclusive club of cronies (soon to be lamed as well), drastic measures are required if at all possible. When Esav realized who he was dealing with (even though he was 100% non-spiritual and could not believe in Gd) he understood the practicality of moving a bit further.
So why spend so much time on recounting all the descendants of Esav, two major alias 6 and 7 including Musaf! Esav is a goof! Well that goof was the chosen "look" for the world, the perfect "animal specimen", question is weather he will get a breath of spirituality... ever. When that day comes, Gd will have completed one of the major feats of creation. So yes, a certain importance is given to that "branch".