I am curious what convinced you they were wrong? Who teaches you now to deny what has been the historic Christian understanding of the triune nature of our God? I certainly don't claim to be able to comprehend everything that this doctrine entails - we have finite minds incapable (for now) of grasping the infinite. This is something we accept by faith because it is what God has revealed to us in His word.
Throughout my youth and adult years of attending a Trinitarian church, I was sometimes curious as to why the pastor would seem to dodge certain parts of the book of Acts. But he was just teaching as he was taught. (While driving this week, I heard Allistar Begg cleverly dodge, and horribly misinterpret passages in Acts. He teaches as he was taught, no doubt.)
It wasn’t until one of my younger brothers moved away, and only months later told me he had been baptized in the name of Jesus. This seemed odd, since I had only heard of folks being baptized in the triune formula, myself included. He pointed out that the only way that folks were baptized in the original church, in obedience to Matt. 28:19, was in the name of Jesus.
The words and works of the apostles testify to that fact. Further study revealed to me that the Son indeed inherited his Father’s name (in fact inherited all things from the Father). The Son testified that the Holy Ghost is sent in the name of Jesus.
That was the beginning of seeing the way of the Lord more perfectly. Even you admit to not being able to completely comprehend the trinity concept.
Look at this crude ‘Ironman’ comparison. (disclaimer: I have never seen an ‘Ironman’ movie, but have seen enough clips and info to understand the idea it is built on.)
Ironman is supposed to be a suit with amazing powers, even AI is built into it. It’s creator dwells in it, and out of it. It has full function capability autonomously, thanks to the AI, but only doing the will of it’s creator, never using it’s AI to do anything contrary. Although, I’m told that in one of the movies, one of the creator’s suits goes off on his own, but has a change of ‘mind’ and returns.
Jesus Christ claims to have received EVERYTHING from the Father; words, works, love, feelings, ability to create,, his very life. The book of John testifies to that. And the Son testifies that the Father is in him, and he in the Father, literally. The Son was sent in the likeness of sinful flesh, even having to deny his own will (which wants to follow the desires of the flesh), and instead do the will of the Father.
Man has chosen to believe that the Father is not literally in Christ, looking at the Father and Son in a carnal understanding (hence the false testimony of Joseph Smith, who claimed to have seen, and spoken with, both the Father and the Son).
**This is something we accept by faith because it is what God has revealed to us in His word.**
God has revealed in his word that the Son received his words and doctrine from the Father. The Son came not to bear witness of himself, but to bear witness of the Father. Jesus Christ said the Father gave the words to speak and the power to do the works in order to bear witness that the Father sent him. That is pointed out quite well in John chapter 5.
God, the eternal and invisible Father, is revealed to us through his Son. It is that simple.