Trinitarianism is the outgrowth of the early Christian Church coming to terms with the Jesus Event and all of its ramifications. That Jesus was in some sense identified with the God of Israel is found in the New Testament itself, what followed in the next few centuries was trying to make sense of this. Various competing theories existed at various times, some forms of Adoptionism posited that Jesus was adopted as God's Son and became Divine in His resurrection. Modalistic Monarchianism (also called Modalism or Sabellianism) stated that Jesus was the Father appearing in human likeness. Arianism said that Jesus was Divine, but was a lesser divinity, a second God created by the Father to function as an intermediary in the act of creation and redemption, a Demiurge.
Ultimately Trinitarianism was the result of early Christians concluding that these different theories just didn't work, they all failed at some level to describe the full impact of the Jesus Event. Following the specific Christological arguments in the early-mid 4th century between the Nicenes and Arians, the debate moved over to question of the Holy Spirit. The Holy Spirit had long also been understood to be distinct from the Father and the Son in some sense, being at times identified with the Wisdom of God such as that Theophilus of Antioch spoke of the Trinity as the Father, His Word and His Wisdom.
It has nothing to do the Father needing help (or needing anything whatsoever); but has everything to do with making sense of the Event and experience of Christ and the Spirit in relation to the understanding of God in the ancient Christian community.