Rashi in the beginning of this week's parsha notes that the space that the sefer Torah normally leaves in between parshios is lacking between Parshas Vayigash and Parshas Vayechi. He cites Chazal who explain that once Yaakov Avinu passed away, the eyes and hearts of Bnei Yisroel became "closed" due to the burden of bondage, when the Egyptians started enslaving them. Therefore, the Torah symbolically closed parshas Vayechi in reference to the closed hearts of Bnei Yisroel.
Rav Wolbe (Shiurei Chumash) asks, we know that the bondage in Egypt did not begin after Yaakov died; it only began after the very last of the Shevatim passed away. If so, what did Chazal mean when they stated that after Yaakov died, the eyes and hearts of Bnei Yisroel became closed due to the burden of bondage - the bondage did not start until many years after Yaakov died? He explains that the bondage mentioned by Chazal is not a physical enslavement, rather a spiritual bondage. They began experiencing the influence that the Egyptian culture was having on their lives.
As long as Yaakov Avinu was alive, he succeeded in ensuring that Bnei Yisroel remain on the spiritual plateau upon which they had lived when they were in their homeland Canaan. However, when Yaakov passed away, Bnei Yisroel lost the one who protected them from the cultural winds that blew in those days, and the Egyptian influence began taking its toll on their lives.