Actually he's the father of Ninjutsu, not the creator of the whole world. He probably even born after Ten-tails.
But I thought he was considered a god who made the ninja world?He didn't create the ten tails, the ten tails was around even before the sage of the six paths was. That's why it's in a legend that when the world is in danger, a savior will be born and the sage was born with the rinnegan, which he used to defeat the ten tails and seal it in his own body.
he was a monk so why would he claim to be god BAKA's