She ruined mustafa by not always telling him the real situation. Not telling him that he could be put to death if he didnt listen to his father the sultan. instead she made him think that no matter what he was the heir just because was the first born son that lived no matter how many sons the sultan had.
10:46 she did it from begging yes, both Hurrem and Mahidevran were own rights ,palace unhealthy place but Suleiman said "Im not my father" but he killed son