Why believe in the Trinity?
Tertullian cobbled together this ridiculous word salad and was never recognised or beatified by the Church because he became an “heretical” Montanist. His writings were seized on by the Church and made dogma in the 4th Century onwards. They were were welcomed by the nascent Roman Church because the miraculous birth stories and “Son of God” bits just did not stand any scrutiny (just like today) and Tertullian gave an explanation that could be promulgated as fact to all the gentile churches.
The only story that may have held a shred of credibility (if there was a YHWH) was the original “Followers of the Way”, Jewish “christians” who believed that the Yeshua figure was adopted by god at his death because he was “the perfect jew”…anathema to the gentile church of Rome and indeed, the Eastern Churches…
Your credence of the Trinity dogma is as silly as any credence given to the later invention of Hell and for the very same reasons.