90-100ad isn't decades after the death of people it's about.
I'm guessing you are claiming the John lives to be nearly a hundred years old? Even though there is no evidence to support this....
And it wasn't authored anonymously.
Yes... It was. He did not assign his name or identify himself as the author. Most people believe him to be the author through contextual clues as you suggested. These contextual clues first put forth in 185ad have shaped the ways people reintertpred and translated the Bible every since.
Which the writer of John clearly was.
John did not write it.... He may have orally transferred the story to someone who later wrote it down after the time of his death. You're working off of assumptions that are highly disputable.
There are four detailed accounts of Jesus.
From his own cadra of followers...... That's like saying everything scientology claims about L Ron Hubbard is true because it was witnessed by 4 different scientologist.
Mormonism has been debunked by the finding of the "original" papyrus to one of their scriptures. The Qur'an claims to be in agreement with the Bible yet contradicts the hell out of it. Mohammed and JS had numerous wives because "god told me" and Mohammed was a warlord, JS tried to set up "deseret"
And all Christian text are non contradictory.....? There haven't been any ancient scripts found about Christianity that the church hasn't adopted?