As they say... nothing new under the sun.
I expanded on Martyr's point somewhat - starting here..."In the first place [we furnish proof], because, though we say things similar to what the Greeks say, we only are hated on account of the name of Christ, and though we do no wrong, are put to death as sinners “
Historical Jesus - page 2
Personally, I can think of at least a few good reasons for the similarities between various pagan myths/lore and a historical Jesus as described in the four Gospels besides forgery and a related cover-up.
BTW, do you have evidence for this supposed conspiracy?