Legion
So Osirus wasn't ressurected, he was reassembled?
For god's sake think harder.
I don't have to think, having read the primary sources. Please cite any ancient account of Osiris' death in which he was said to have died and was resurrected (rather than be put back together except for his penis, an integral part of the main variant of the myth). Then you can try to find actual sources for whatever you have or haven't read online or in popular books on the modern, made-up "death & resurrection" stories about Attis, Mithras, Adonis, Dionysus, Orpheus, etc. You may even find, as has long been known, that many of the cult traditions centered around figures popularly compared to Jesus in order to provide evidence for the Christ-myth theory were influenced by Christianity.
We've come a long way since armchair historians like Frazer and the unscientific psychoanalytic theory of Jung. We have more evidence, better methods, more disciplines, and far more experts (among other advantages). Frazer, an extremely erudite individual writing at a time when most of the methods and many of the fields which are used in historical research didn't exist, spent years re-writing his central work in order to make it defensible even then. That was before decades of study in fields as diverse as Homeric studies and Folklore studies to anthropology and cognitive science were incorporated into research on ancient history. Modern linguistics, invaluable for analyzing our texts, didn't exist. Neither did the fields of social sciences which have proved invaluable for understanding the socio-cultural matrix out of which the Jesus movement grew and subsequently Christianity. Archaeological, epigraphic, and even manuscript evidence was paltry and pathetic compared to what we have today.
Now, we have thousands and thousands of manuscripts from in and around the first century. We have abandoned the idiotic, unscientific psychoanalytic bunk along with the Marxian-like teleological models of history from armchair historians, a central basis behind the attempt by some scholars to make analogies and parallels between
mythoi ~100 years ago. Such junk is relegated to websites and sensationalist drivel published by those like Freke, Gandy, Doherty, Murdock, etc. When the notion that Jesus likely never existed was still being actively debated among scholars in the late 18th and most of the 19th century, our knowledge of Greek was so inferior that philologists, classicists, and biblical scholars believed the Greek of the NT was unique (and therefore possible evidence of divine inspiration). Just as that bunk has been demolished, so to has the idea that superficial parallels between Christian tradition as espoused esp. in the NT and Greco-Roman myth, frequently made without reference to actual sources and/or to sources which postdate all the gospels, meant Christianity must have borrowed from paganism. It turned out that there was no "paganism" to borrow from in the way thought, as religion in that period was a matter of practice and indistinct from other private and public spheres of life, and that borrowing went both ways. Christians stole heavily from philosophers like Aristotle while pagan cultic traditions borrowed heavily from Christian doctrine and theology.
I won't bother to do what real historians do here and refer to actual scholarship, as you apparently think that the entirety of academic practice is a sham (whether it is physics of philosophy) because you equate citations of expert literature with fallacious appeals to authority. Instead, I'll ask you again to produce a shred of evidence for your claims. What documents can show demonstrated this "common theme" from which the Jesus movement
could have borrowed, and then why the Jewish matrix out of which it grew makes any sense if based on such a "theme".
In short, do what you said you could & would:
Well the whole messiah, death and ressurection thing is a pretty common theme for starters. I'd be happy to elaborate.