pretty much because of everything he experienced, he realized that it helped him to attain understanding as experience is the best way to approach understanding of reality to be enlightened
well starts out as a brahmin, then he leaves that life behind to be an ascetic with his friend, but they leave that behind when they find out that the buddha is nearby. den his friend stays behind with the buddha and siddhartha goes and becomes a business man for like 10 years. he gets sick and tired of that life and up & leaves to kill himself by the river and that's when he heard his innervoice sing with om and he sleeps for 2 days by the river and he feels reborn and becomes a ferryman & listens to the river laughing at him, etcetc
oh yeah when his son leaves him, he finally feels the sorrow of love & he has a deep compassion for humans because he could never love~ anybody before
