Monsignor Pope Ping!
This is like asking why is the son, the son?
People seem to get really confused about the tri part concept
Need to remember human being are created in the image of God and when we say “image” we’re not saying we go look physically like God
We say we are created in the image of God it means we are also tripart beings... we are the only living thing on this planet that is of three parts...
If you really want understand the trinity look at yourself as a three-part being and try to understand..... we are a spirit and we have soul and we have a physical manifestation
I have never tried to figure out the Holy Trinity; I just accept It. If It was too much for St Augustine on the beach to comprehend, I don’t feel backwards in my understanding. :)