God is the Creator of everything. The only Jews who knew God were the prophets. All the rest of the Jews were clueless of who our Creator was so they could only believe what the prophets said, which most of them didn't. Most of the prophets were killed because of their testimony to the Word of God, and I'm not talking about the written scriptures.
Only us saints received the knowledge of God to know what happened during this age and where God's people will be in the future. Only chosen believers will believe our testimonies.
So why did God not try to spread the word then?
Since none of God's people will remember this first age, it doesn't matter. Besides, unless you're a chosen believer who listens to the gospel we saints preach, the rest of the world wouldn't understand it anyway. The gospel was only meant to find believers who carried some thoughts God needed to help clarity our understanding. The other reason for the gospel was to split people up into believers and unbelievers. The unbelievers get jealous of the saint and all his believers so they have the saint and even some believers killed.
This is what this prophecy is all about;
Revelation 6
9: When he opened the fifth seal, I saw under the altar the souls of those who had been slain for the word of God and for the witness they had borne;
10: they cried out with a loud voice, "O Sovereign Lord, holy and true, how long before thou wilt judge and avenge our blood on those who dwell upon the earth?"
11: Then they were each given a white robe and told to rest a little longer,
until the number of their fellow servants and their brethren should be complete, who were to be killed as they themselves had been.