To be fair, being a Christian (an actual Christian, not what 99% do and using the term to excuse their opinions and actions) means being like Christ.
So Christ had to be a Christian since it means being like him.
Edit: I wanna add that you can be a Christian without following the religion that exists. Being a Christian boils down to being a good person and helping others.
Who even uses that definition outside of super niche communities?
So a good person who behaves like Christ but grows up in a rural village and has never heard of Christianity or read the Bible would be a Christian under this definition?
Nah, he was Jewish, he had to be to fulfill the Jewish scriptures he claimed proved he was god. He literally called himself the King of the Jews. Even according to Christians, people didn't invent Christianity until after his zombie corpse died again.
Like, Buddha couldn't have been Buddhist, we based Buddhism on him.
Also, if 99% of the members of a group agree on what membership means, it's the 1% that disagree who aren't really members. Maybe consider changing what you call yourself if it's at odds with 99% of the people calling themselves that.