expose! (joseph's story)

one of my Bible study lessons i had with one of the
Crusade (Nus and Ntu combined batches. about 3 batches combined)
our group did the study of Joseph.

His brothers did not love him at all. (some because of jealousy, some because of
anger at their father's lack of fairness). But of course, some were good.
That was just the childhood/teenager stage.

Throughout their lives, some were up to, well, a lot of immoral stuff and some had
serious anger issues, due to the same reasons mentioned above and other reasons
(envy of favour from the father, rights).
At the end of Jacob's life, he finally exposed and scolded his sons' wrongdoing
(not all were scolded, some were righteous). And gave them a character summary.
(kinda amusing yet...shocking)

I wonder why Jacob knew everything but didn't talk about it or correct them till
the end.