The proto-trinitarianism of the Christian Testament and Trinitarian theology aren't the same thing. Proto-trinitarianism understood Jesus as the Messiah doing God's will, and the Holy Spirit as the authoritative Spirit in Jesus and the church. Trinitarian theology emerged in the 300s to identify God as Father, Son, and Holy Spirit. Trinitarian theology isn't in or from the Bible. It's the result of 300 years of reflection upon the Bible. Theology is meant to evolve, not get stuck in the past.