My initial comment: 

interesting question, but I am not sure if I understand it at all. It took earliest Christians more than 400 years to somewhat agree on the nature of Jesus as Son of God. As it has been pointed out, the reason why the early church survived has little to do if they believed in resurrection but more with political factors – i.e. how successful the perfect Christian organization took over a failing and degenerating West Rom and became state religion of East Rome by Roman Emperor Constantine. Even then, the remaining dissent (https://stottilien.files.wordpress.com/2012/05/christological_heresies_in_jesus_human_divine3.jpg) about Jesus’ nature supported the rise of Islam (for which Jesus is a minor prophet and do not believe in resurrection) as the Monophysites and others were more comfy being Dhmnis than Byzantine subjects. Some of my little knowledge I derived from the book “The lost history of Christianity – from Philip Jenkings.

In regards to the quote Lucan (the physician in Antioch) authorship of the Acts is widely held, therefore it is useful to be examined in conjunction with the Gospel of Luke (my favorite Gospel anyway). Luke’s description of “Ascension of Christ” has a very important function in the Lucan work, told twice. The Gospel closes with the assumption of Christ and the Acts of the Apostles start with it. Behind this is a formulation of the early beliefs that Jesus was resurrected and raised to God.

Which led to an interesting discussion.

Daniels  remark “We could explain the expansion of Christianity under the rule of Roman Emperor Constantine the Great (306–337) as political but that would not be true for first Christian movement.”

 I politely disagree; the history of Rome (and the Catholic Church) tells exactly that story. Let me elaborate what I meant with the perfect Christian organization took over a failing and degenerating West Rom. This story of the Church’s success started (AD 37) around the last years of the reign of Tiberius who a that time already lived at Capri to enjoy his pervert lifestyle. The empire was stretched from England to Africa and from Syria to Spain, its borders calm the vast majority of earth lived under Roman law and paid contribution.  But the core was already rotten, the enormous wealth leads to a corrupted and decadent upper class and an alimented and circus entertained Roman underclass (slave work was cheap) and sophistication mixed with brutality terror, tyranny and greed.  After Tiberius’ death, the crazy Caligula took over, then the weakling Claudius and then the infamous Nero. Except some bright spots, the situation only became worse in the next 300 years until the empire faltered und the Roman church took over the spoils.

 Daniels  remark:  My question is not if early Christians agree the deity(or dual natures) of Jesus of Nazareth, but how do we explain the first Christians movement, if we deny resurrection?

 Thanks, here is the misunderstanding on my side.  As a Christian I would never deny the resurrection as a central message, but my assertion was it was not the only and not the only factor of the church as an organization.

 Earlier to Lucanian account is Pauline quote(in 1 Cor. 15) of early Christians’ poetic hymn, which Historians both, Christian and non-Christians date it 2-5 years after the crucifixion of Jesus from Nazareth(C.H. Dodd, The Apostolic Preaching and its Developments (New York: Harper and Brothers, 1960), 16.) :

 Daniels remark:  How to explain the first Christians’ movement if we reject resurrection hypothesis.

 That I am afraid you have to ask a pagan. I even pointed out in my last post that in the Lucanian writings death and resurrection of the Nazarene was of first importance. For the reasons of fulfilling prophesy (here what he said to his followers about his death and resurrection) but even more as he did for our sins exactly this gave us back the promise of eternal life. Having said that, other offshoots like Islam quite flourish (in numbers) denying any claim of resurrections. For the early Christians it would have denied them the central message of hope and most likely would have stayed in despair of the Messiahs death…

 The success factures of the Christian church as an organization are two folded

 1) External success factors, the early followers used the globalized infrastructure (streets, common languages Latin and Greek) a revolutionary situation with brilliant apostles, an   appeal to women, slaves and other disfranchised which had more clout than the eye met. This, together with learning and taking over a centralized global administration from within was the core reason of establishing a central Roman church organization which exists today.

 2) There were however, also unique selling prepositions (USP) of Christianity together with a superior quality of the Christian core teachings of the Apostles (e.g. Gospels). The Christian message is one of hope, but it has been multidimensional to some Jesus was the prophesy fulfillment of the messiah to others the promise of eternal life promised by the resurrection. As the pagan Seneca said: “Show me one being resurrected and I believe in eternal live”. But that was not all, I would agree with Henri Daniel-Rops (The church of apostles and martyrs), even more important was the Pentecostal event and the Sacrament of communion.  Also the incredible uniqueness up today of the dual nature of Jesus: he was not man, he was not God but both – a union of two natures as undiminished deity and true human in one person forever, inseparably united God being fully God and man being fully man in ONE person forever. Jesus died as human for us and this gives us eternal life back. The image of a Christian god was one of unconditional love, not the punishing Yahweh or the many polytheistic manmade creatures before. A prior very recently explained me, that the Christian god can be seen more as mother than of a father, which almost annoyed me (my first association was the goodness Kali). But it’s true, that was exactly the reasons for the initial appeal to the powerless.  Furthermore the message was refined and blended with Greek philosophy (e.g. the concept of an eternal soul came later and originates entirely on Plato and Plotinus.  

Summary: The message of the Resurrection of Christ is important, even a crucial last stone in the church but  not the only reason for success of the first Christians’ movement or if denied its compelling and mandatory failure:

http://wp.me/s2bcCT-3671