Yeah. They admitted they wanted to eliminate all humans inside the walls. But that doesn't seems very true if we remember they had the chance to do it two times. They could have continued the attack and breach the 3 walls. So there must be a "reason" for them not fulfilling an 'apparently easy'...
This chapter explains a lot of things.
Frieda
She inherited the coordinate and the King's will and was constantly tormented by it. In the night Grisha came to the cave, she would probably hand over her power to some of her brothers because she couldn't live with anymore.
The first King...