Why did Yosef weep over his brothers?
Rashi: Refer to 45:15:2:1.
Targum Yonasan: Because he foresaw that that they would be enslaved among the nations.
Why did the brothers not speak to Yosef earlier?
Rashi: Because until now they were embarrassed, and it was only after they saw the extent of his weeping and that he bore them no grudge that the barrier between them was removed. Ohr ha'Chayim - Until now, they thought that perhaps he bears enmity; all his words were to spare us shame. Perhaps his crying was due to his pain, or over separation from Binyamin. After he hugged them and cried over separation from them, they realized that he is a faithful brother.
Ha'amek Davar: They were astounded to see his dream fulfilled. They thought that perhaps he understands that they will permanently bow to him, i.e. they will be his slaves. After he kissed them and cried over them like a brother, they understood that he holds that the dream was already fulfilled, and he is no longer a master over them.
