Why Iglesia ni Cristo members dont believe in holy trinity?

The Holy Bible clearly states that Christ Jesus is a man, which is made of flesh and bones, while the Holy Spirit is the Comforter whom God has sent to help human beings in times of trials & tribulations and help the servants of God in remaining strong in the faith. And so, how can Christ Jesus be God, when he is made of flesh and bones, and God is a spirit? How can the Holy Spirit be God if God sent the Holy Spirit? There is only One True God, and that is the Father in Heaven, not including the Son and the Holy Spirit.