>lets say the nobody is revealed and they boldly state they are jesus christ come again and that christianity is the one true religion and everyone else was wrong and dumb
>what happens next?
I'm not going to engage in those kind of hypotheticals. However this will ruffle some feathers.

Between Apostle Paul of Tarsus and Jesus Christ, which one of them successfully rose from the dead and came back to life? So whose teachings and guidance should a Man of God follow and heed first?
Jesus Christ provided what is needed on how to worship, love and obey God. He also gave us more, that being grace for our sins and the ability to call on his name during prayers to God, something which was not available before. The Son of God spilled his sinless blood for us to give/bless us with that and more.

Now Jesus Christ in the Revelation came to his picked Apostle John and told him to write of the seven churches, their doings, mistakes, sins and cautions and warnings.

The folly of the Egyptians: universal idolatry
But they are the craziest of all,
and poorer than the soul of a weak child,
those enemies of your people
who once oppressed him.
Because they worshiped all pagan idols
who can't even see with their eyes,
neither breathe with the nose, nor listen with the ears,
can't touch with fingers,
can't even walk.
Because man made them,
they are created by the one to whom the breath is on loan.
No man can do it
similar to God; and because he is mortal,
ungodly hands build a dead work.
He is more precious than his saints,
because he is alive and they are not.
And they worship even the ugliest animals,
which, by their stupidity, are worse than the others.
No beauty on them
to attract like other animals:
they escaped both God's praise and his blessing

BOOK OF WISDOM about ROG WORSHIPERS.