Revelation 20:4

[Bucky Ball]

I've watched the Jaclyn Glenn's video "Christianity Disproved" a few years ago (actually, I think it is even before I started learning Latin) where she shows how the story of Jesus appears to have taken elements from earlier ancient mythologies.
https://www.google.com/url?sa=t&source=w...K16PCch7F2
Are you referring to those kinds of things? I think there is some truth to that, but that the basic idea of Christianity is completely original. The basic idea of Christianity is that God got angry at the humanity and had to sacrifice his own son in order to forgive us. As far as I know, that doesn't fit well into comparative mythology.

That's not accurate, sorry to say. That was not the "basic idea" of Christianity. Jesus never claimed that, and the first Christians were JEWS. The role of a Jewish Messiah was NEVER to die for sin.
The disciples in Acts ask Jesus "Wilt Thou O Lord, at this time restore the Kingdom to Israel" ? THAT was the role of a messiah. The Jewish rabbis started talking about how to preserve Judaism after the temple was destroyed, in the late 1st Century and they came up with "love God and love your neighbor". The concept existed in other Far Eastern cultures prior, but not in Judaism. The rabbis wanted to simplify all various rules and regs regarding for the Diaspora dealing with no temple. Jesuds told them "not a jot or tittle" would be changed until all things were accomplished.
Jews didn't need anyone to die for sin. They already had a sacrifice system that took care of their sins just fine. That did become a problem when the temple was destroyed, but if there was a Jesus in the early 1st Century it was not one something he had to be concerned with. When the young Matthew asked him what he had to do to gain eternal life, did he tell him "Just you wait, I'ma die for your sins" ? No. He said "keep the commandments".

The  basic ideas in Christianity (which the Christians developed for decades, ... actually centuries) ... you can "watch " happening if you read the proceedings of the Councils (Fordham University's web site) was not what you claim. What you claim is refuted in the gospels themselves and Acts. 

The preaching content of the gospels reflects the concerns of the Jewish rabbis at the end of the 1st Century, post temple destruction as many of them wrote about, (and which you have obviously never read). "Love god and love your neighbor" was not in any way original to Christianity, AND we know that the members of the Jewish "Way sect" (early "Christians) were still Jews until at least the end of the 1st Century when the Jewish High Priest required the "Benedictions against the Minim" (the "Expulsion Curses) (as mentioned in John's Gospel, to be read at the end of every synagogue service. In the year 400 CE, the Archbishop of Constantinople told HIS Christian congregation to stop going to synagogue (Christmas sermon they still have).

https://www.youtube.com/watch?v=LTllC7TbM8M&t=318s

There was no Christian "orthodoxy" for centuries, thus no (singular) "Christianity".
When Constantine called the Council of Nicaea he told them they had to "agree" on something, but he didn't care what they agreed on.
Christianity before that was fragmented and very diverse.

https://www.youtube.com/watch?v=Jv3iOS69Uws&t=32s