Perhaps we can answer the question as follows ,Bezrat Hashem: There are many events that happen during a persons life span.......At times these happenings seem very inexplicable and confusing to us...............We often wonder "why" or "how"....................Yet we trust in G-ds infinite wisdom and rely fully on His boundless Kindness, and realize that its all for the ultimate good..............However, we rarely can trully understand the reasons behind the events of our lives...................When Jacob finally saw his son Joseph, Jacob had a glimpse into the reasons for his (Joseph) disappearance, namely (1) Joseph was a means by which the world was saved from a most devastating famine,and(2) this was the beginning of Israels enslavement in Eygpt which would ultimately reveal G-ds dominion over the world. Jacob had in essence a glimpse into G-ds ultimate plan, which is a great kindness . When a person says Shema and enunciates the words ("Hear O Israel: Hashem is our G-d) Hashem is One" , that person is actually declaring G_ds Oneness to the world and to himself. The Oneness of G-d means that there exists no coincidences or haphazard events , but that in reality everything and all emanates from G-d Almighty for a reason that is full of wisdom and kindness......... Therefore, when Jacob saw Joseph in Eygpt alive and well(,in addition to be being a ruler ), Jacob had at that moment found it compelling and necessary to declare Hashems Oneness. Hashem had revealed to Jacob the reasons for the events of his life,and was thus overwhelmed by the enormity of the wisdom and kindness of G-d Almighty.................... This is surely a great lesson for all of us when confronted with our own reality.........................Have a good Shabbos