The Trinity is not described by nor is it suggested in any way by either Jesus directly or indirectly in the Bible. In fact Jesus makes it quite clear as to His station and how it differs from God.
There were a number of steps that led to a conclave that then tried to build the case for the nature of Christ being part of the Godhead. This may have been in error, or an innocent tangle of abstract concepts, or to appease an emperor, or it may have been to deliberately elevate Christianity above all other religions.
You have billions of humans where billions are billions. You have the eternal Oneness of God. Three can only become one in faith based beliefs that are devoid of logic and reason.
