Because Jesus, my Lord, my God, my All, established a Church. Cata-holos. It’s a continuity thing.
"So why do you need a Pope, priest, bishops, etc.?"
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God chose to use people to teach His teachings to others.
God did not NEED to use "Matthew", "Mark", "Luke", "John", "Paul", "Peter", etc. as middlemen to teach you about Jesus. God could have taught each of us directly, not using anyone else at all. However, God CHOSE to use other human beings for that purpose in His Sovereign Holy Omnipotent Will.
YOU and I, however, DO need to use the work of those middlemen God chose in order to learn about Jesus.
(That is the way God wanted it, and chose to do it.)
God set up His Church to continue that same teaching function, and He said the gates of hell would not prevail against His Church.
It is just like creating new human beings -- God can make human beings (Adam and Eve) without making use of other human beings to do it, but God usually chooses to make use of existing human beings to play a part in bringing other human beings into existence.
Why do you need a congregation, a pastor, preacher, minister, choir, seminary, or Bible college? Isn't the bible given you by His Church all you really need?
Pax et bonem