I'm afraid we can't blame the doctrine of the Trinity on the Catholics or on any old myths that happen to have three of something.

Jesus himself made it very clear that He and the Father were one and He referred to himself as the Son of God.

For God so loved the world that he gave his one and only Son, that whoever believes in him shall not perish but have eternal life. For God did not send his Son into the world to condemn the world, but to save the world through him. Whoever believes in him is not condemned, but whoever does not believe stands condemned already because they have not believed in the name of God's one and only Son. This is the verdict: Light has come into the world, but people loved darkness instead of light because their deeds were evil. Everyone who does evil hates the light, and will not come into the light for fear that their deeds will be exposed.