The question is absolutely crucial, although there may be no clear cut answer. My answer is to remember that Christ only had a sense of indwelling with God, whom he called Father, to inspire him. He called his disciples friends, but they all misunderstood him. He had no-one in whom he could confide; no-one of whom he could ask advice. Whereas his sense of a communion with God must have been almost overwhelming. Otherwise he was entirely alone. It is absolutely obvious that he was telling us about the nature of God, as he knew it. He had no interest in the wealth creation of society.
As regards the secular world, his experience was very limited. As a boy he went to Egypt, as a man to Tyre; he had seen little of the world. He can have had no concept of the Empire, nor of the Roman Army, nor of the organisation necessary to sustain both. Nor can he have pondered the question why Rome was able to bring peace, when Greece for all her genius had failed. His deep study was of the scriptures: not secular history. His worldly knowledge must have been entirely parochial. Indeed without Paul’s cosmopolitan reinterpretation, Christianity would have lived and died an obscure Jewish sect. It needed Paul to convert it into a world religion. Jesus had no experience even of running a community, or wealth creation beyond the carpenter’s shop. If it is said he had the experience of his disciples for three years, they lived on the charity of rich women. Many of us would say that was not a creditable way to live. Where his teaching soared above his contemporaries was in his knowledge and understanding of the scriptures, in the authority with which he spoke, and in the freshness of his message; although one must remember that much of the Sermon on the Mount was current thought at the time. Only a fool lectures on subjects he does not understand, and Jesus was anything but a fool. It is absolutely obvious he taught men about the thing he knew supremely well: the nature of God, and man’s proper relationship with him.
The inevitable result was that his Kingdom was other worldly. Maybe the might of Imperial Rome dictated that anyway. But his sense of communion with God and the absence of any comparable human intimacy made it inevitable, unless he were to indulge in the wildest and most foolish egotism. He did what he could with the means available to him. And what he achieved, from any point of view, was truly remarkable. But he did not have the benefit of an indwelling with a member of mankind as well; that would have meant that his gospel would have embraced that other person. It would have embraced this world, as well as the next. And it may be that to those who have an indwelling with God and an indwelling with man, greater things are achievable, as Jesus himself predicted. But that is to stand on the shoulders of giants, as Isaac Newton said. It might even have disabled Jesus from being the Messiah. His kingdom would probably have resembled Augustine’s City of God: living beside the City of Rome, nourishing it, sustaining it, even rebuking it; but not challenging it. Jesus only had God, so his kingdom had to be other worldly.
No doubt he was very intelligent. He knew the scriptures, and he had the supreme conviction that he had a communion with God, in which he was probably right, and the belief that he was the Messiah. That will have enabled him to bring a fresh intelligence to bear on the scriptures; and with Divine inspiration, and a complete absence of egotism, he will have been able to work out correctly the salient features of the Messianic mission. Otherwise he was like us, in body and mind. He had no magical powers.
The views Jesus held on astronomy were extremely crude: the stars were going to fall in the day of judgement. But that does not alter the fact that Newton’s theory of gravitation was a better hypothesis than that of Ptolemy for describing the heavens. Nor does it alter the fact that Einstein’s field theory of gravitation is a better hypothesis that Newton’s force theory. Almost everyone recognises that it would be pathetic to dispute the considered judgements of science, and to prefer the crude views of Jesus on astronomy, because science is recognised as truthful; (although I have been surprised and dismayed to be told that the amount of deliberate dishonesty in scientific research nowadays is alarming).