You got sources or an explanation for why that is?
I agree largely with your leading post on this thread. Christianity does indeed resemble Zoroastrianism much more than Judaism. The God (or Gods) of Zoroastrianism and Christianity are nearly identical. Both religions are structured on the classical Indo-European model dating back to perhaps 8000 BCE in the original Indo-European Homeland before the migrations.
Both religions have saving grace, a virgin birth of a saviour, a Father God, a Holy Spirit, a resurrection, a devil (or evil God of Darkness, Angra Maingu), a communal meal (Eucharist), a ritual eating of the saviour in the shape of a Solar Disk of bread, an Armageddon or Final Battle of Light versus Darkness, and a final judgment.
This obviously has little resemblance to Judaism, which gave rise to Islam.
Indo-European Religion is not recorded in writing but a proto-Religion of the Indo-Europeans can be deduced by the history that Indo-Europeans migrated from the area north of the Black Sea in a series of migrations. They went East, South, and West. The ones who went east included the Indo-Iranians (Aryans). Their major surviving religions are Hinduism and Zoroastrianism, which have obvious similarities.
Those who remained in the ancestral homelands included the Scyths, Sarmations, Alans, and Iasgians whose religion is little known but who spoke Indo-European Languages.
Those who went south (Achaeans, Hittites, Luvians, Lydians, and Phrygians) left little reliable descriptions of their Indo-European religion but they left Indo-European Languages.
Those who migrated west (Celts, Italics, Teutons, Illyrians, Greeks, Balts, Slavs, and Thraco-Cimmerians,) who had classical Indo-European Religions showing a clear resemblance to the Eastern group (Zoroastrian and Hindu.)
That means that we can construct a basic Indo-European Religious Template that fits the beliefs of Indo-Europeans that migrated to the Atlantic Coast and the edge of China.
Considering this, Christianity is clearly one of the Indo-European (Pagan) Religions. Christian linkage to Judaism is more of an illusion than a fact. I think it was cultural and religious syncretism that produced Christianity.
Jesus may or may not have been a real person. I tend to think that he was real. He was a prophet, healer (sorcerer), teacher, counsellor, and reformer. He never claimed to be a god. He did have followers who lived in the eastern Mediterranean Region. Over the first two centuries, Pagan converts to various Jesus Cults. Those Pagan Indo-Europeans (Romans, Celts, Greeks, and Anatolians) brought with them the baggage of Indo-European structured religions.
This religious syncretism led to the gradual belief that Jesus was a god similar to Mithra, Sol Invictus, Lugh, Lieu, Odin, Apollo, and Helios. This process (apotheosis or deification) was not sudden but slowly over three centuries. Jesus EVOLVED from a prophet to a secondary God to a full-fledged God. (Athanasian Christianity grew in the fourth century CE.)
For Jesus to be an Indo-European son of God, a Father God was needed. JHWH seemed to fit the bill. God (perhaps the Holy Spirit or Messenger God) conceived Jesus in a Virgin. Thus, Athanasius and Tertullian had a classical Indo-European structure of Father, Son, and Holy Spirit.
I do not think Constantine merely invented this Christianity. It occurred so slowly that the transition was barely noticed. All that Constantine did was recognize that Athanasian Christianity was very similar to his own Indo-European branch of the Cult of Sol Invictus. When he convened the Council of Nicaea in 324 CE, he felt that he was not making a new religion. He was merely combining the Empire's Indo-European Religions under the banner of the growing Christian Indo-European Hybrid Religion.
IMO, this is why Christianity was so casually accepted by so many Celts, Teutons, Illyrians, Greeks, Romans, and various Anatolian provinces.
In a similar fashion, Christianity spread by the Spanish in the Americas by absorption of Native American religions and gods. Native Americans in Peru, Yucatan, Columbia, and Bolivia worship the Old Gods as well as Jesus Christ.
Amergin