Book One: Athena Inspires the Prince

I found it interesting how Homer chose to open the book with a summary of the current situation in the form of a council of the gods. It reveals information that is not revealed to Telemachus until much later. What I wondered is if Hermes told Aegisthus what would happen if Aegisthus stole Agamemnon's wife, why did Athena send Telemachus on a quest for information? She could have just found a way to prove it to him. I understand why it occurred, however the huge transformation in Telemachus seems sort of unbelievable to me. After one short talk with Athena, Telemachus went from a weak, submissive, grieving boy to a man who stands up against the plague of suitors and commands his mother to return to her rooms.