Mithra, Dionysus, Orpheus were saviour-gods which pre-date Christianity. Mithraism was one

Mithra, Dionysus, Orpheus were saviour-gods which pre-date Christianity.
Mithraism was one of the major religions in the Roman Empire before
Christianity stamped it out due to its intolerance.  Mithra was said to have
been born miraculously in a manger, died and rose from the dead, and his
followers drank his blood and ate his flesh (compare this with the Christian
Eucharist).  He was a saviour-god, along with many others hundreds of years
before Christianity.

Muhammad did no miracles according to the Qur'an.  You need to quit reading
about other religions from a Christian perspective.  And, what about the
miracles performed by Gautama Buddha, or even Joseph Smith?  What about the
miracles in the apocryphal books?  What about Hindu miracles in the Vedas and
Upanishads?  Why are these "myths", and yours is the "truth"?  Quite biased!

BTW, Polycarp was -not- a "secular" historian.  He was a Christian historian.
"Polycarp can support the resurrections of Jesus and biblical information can
be archaeologically substantiated" only means that the Bible contains history
in it, many real places, and
many real people.  But, none of this means that it is the Word of God.  So
does Homer's Illiad and Oddysey, but that doesn't mean everything in it is
true.  You are saying that just because the Bible contains history, therefore
it is the Word of God.  That could be claimed for the Qur'an,  Vedas,
Upanishads, Gnostic Gospels, Mandean (John the Baptist) texts, let alone
non-religious texts such as histories by Xenophon, Seutonius, Josephus,
Tacitus, Thucydides, or whoever else I can think of.

Alexander the Great was a real person, but that doesn't mean he had a
miraculous birth according to history/myth.  Perseus was a real person, but
that doesn't mean he was born of Diana and Zeus (I think) miraculously.
Apollonius was real but that doesn't mean that Apollo caused a miraculous
birth.  Myths and legends surround all major figures in history.  Why must I
accept yours and reject others?