"Kikoho!" At some point, Tien Shinhan had appeared above Frieza with his hands in a triangle shape aimed at Frieza. A triangle-shaped Ki attack carved hit Frieza and carved out a triangle-shaped hole below. Tien Shinhan's Ki was just too weak to hurt Frieza, but the Kikoho had strong momentum and pushed Frieza crashing down into the triangle-shaped hole.
Because if he did not act like Goku there would be no Saiyan or Frieza saga because of that no super Saiyan and in this time he would train with master Roshi in the order and become very close friends with krillin and when Frieza kills him bammmm super Saiyan.
Then suddenly he thought something he turned his neck and slightly and saw him having a tail!!! He was so happy meanwhile he was sad too because he couldn't meet his family if he was reincarnated, Bammmm... he had an idea he could collect the dragon balls to help him meet his family again, but he was a kid. So, Goku's power level was low so he needed to train.