Ultimately, I believe scripture would say that they were stubborn because they were people. Their education and position had nothing to do with their rebellion against God. They were rebellious simply because it was in their character.
This nature isn't limited to the Jews only, but also to everyone in the world. As Paul says in Romans 3:9-18:
What then? Are we Jews any better off? No, not at all. For we have already charged that all, both Jews and Greeks, are under sin, as it is written:
“None is righteous, no, not one;
no one understands;
no one seeks for God.
All have turned aside; together they have become worthless;
no one does good,
not even one.”
“Their throat is an open grave;
they use their tongues to deceive.”
“The venom of asps is under their lips.”
“Their mouth is full of curses and bitterness.”
“Their feet are swift to shed blood;
in their paths are ruin and misery,
and the way of peace they have not known.”
“There is no fear of God before their eyes.”
This rebelliousness and stubbornness of people is the foundation for why Christ came to die. We were rebellious and did not love Christ, but He loved us anyways, so he came to die to pay the penalty for our sin.