IIRC according to some contemporary document the romans, shortly after killing Jesus, went around to his relatives and friends and planned to kill them too because they thought his teahcings were about political resistance to Rome, but the romans eventually realized it wasn't a political movement but more of a philosophical or religious, and that his kingdom "wasn't of this world", as it was expressed, which implies that his kingdom of heaven was mostly religious and/or philosophical. There's still room for many different interpretations though. Is it the Buddhist idea that much of how you interpret the world lies in your own mentality, and a form of escapism by forming heaven in your mind to be able to survive a life under roman occupation? Or was it a form of religious belief in an after-life in a heaven? Or a belief of rebirth like in Hinduism or Buddhism, that you yield something even if you die, by being transformed into earth, in which things will grow? Those things aren't clear, but it seems pretty clear that Jesus kingdom of heaven wasn't under any circumstance an empire even remotely resembling Rome.