This is why Jews are Jews and not Christians, among many other reasons, but I don't think I ever really learned the historical reasoning for the rejection at the time of his death. Whether you believe Jesus is the son of God, he was a real person.
I just don't understand how and why exactly they didn't believe he was the son of God, and how they managed to survive for so long not believing it.
Jews thought (and still think) that the Rich & Powerful Messiah will come and who will smite all of their enemies and serve all their interests.
Instead they got a lowbrow, peaceful. humble drifting beggar who was converting Jews to His way. Basically doing the complete opposite of what they expected.
Ties in with the jew concept of god (a petty, jealous, vindictive asshole who basically makes up restrictive laws based on whatever his neurosis is feeling at that given moment - essentially a jew with unlimited power and the ultimate jew power fantasy)
Christ spoke the truth to them (John 8:39-44) and they killed Him for it (Matthew 27:23-25)