Prior to and during. When seen objectively, this is not a bad thing. The Christians took the most beloved of symbols, with all positive connotations, as their own. Knowing that no religion grows in a vacuum (look at the parts of Islam founded on Christianity, and the parts of Christianity founded on Judaism for clear examples) it's not surprising.
True, Christians adopted many pagan symbols as their own, and especially Catholicism to a fault IMO. Additionally "idol worship" is clearly forbidden by the Bible, but I'd digress if I went any further on the subject.
As to you assertion of the linkage of the afore mentioned "major" religions, that also is true. However, neither "religion" has accepted THE crucial element and difference -- the Christ mentioned in the Biblical prophecies AND ergo fullfillment of those prophecies as "Saviour" or "redeemer" of the believer's soul.