First of all, for Christians he has never left us. And promised He never would.
He set up His church while he was here on earth in his spiritual body.
I've explained it to you many times, even on this thread.
How His church works, who it is made up of etc.
Catholics are free to join, the instructions are in the Bible.
Since then most Christians have held to His Cchurch and His truth
Very true! I have changed "church" to lowercase "c" because "Church" is often used as shorthand for the Catholic Belief System and it's organization.
...every generation has it’s Judas who tries to lead others astray
Catholicism started about 300 years after Jesus did his earthly Ministry in a human body.