As I understand it, Christianity was constructed well after the deaths of Jesus, his disciples, Paul, the participants in the post-crucifixion home churches, and others. I presume there was a continuous community who carried their experiences, memories, and collective understandings forward, but they did not "construct" an institution.
The construction crew began work decades after Jesus. At the moment I can't cite a number. The crew had various writings in hand (like Paul's), oral material that was eventually committed to writing--some of which probably came directly from Jesus and the 12. How much? I don't know. They also had a fairly numerous body of 'Christians' (as they would eventually be called) who needed documentation to buttress their faith and experience. There was also a need to establish some sort of organization -- the early 'church' -- but not yet the organization that has come down to us,
The construction crew existed in a rich and varied cultural context. which influenced how they edited documents, what they accepted and what they rejected, and perhaps what intent they wrote to tie the fragmentary documents together. The construction did not take place in Jerusalem or thereabouts.
The thing is, the story of Jesus came together as a cohesive narrative supplied in the Gospels, but the letters of Paul, and by other authors. That's the document -- New Testament.
Thousands of believers scattered around the Mediterranean in the Greco-Roman world had their own local experiences, and over time developed rituals, liturgies, orthodoxies, and heresies.
Eventually the nascent bishop prick of Rome and some other centers became strong enough to promote the right kind of faith and suppress the wrong kind of faith.
So, here we are, after 1500 years+ of never-quite-kept-for-long-peace-and-harmony-in-the-Body-of-Christ.
Christianity Today is being deconstructed through several avenues.
1) millions and millions of people no longer participate in Christian religious activities.
2) scholarship (like the Jesus Project) undermines the historical record that was established by the early church. (This is different than the historical record of whatever actually happened in Jerusalem or on the Road to Damascus about which we have no objective sources.)
3) secularism and secular institutions supply many of the services the church alone once supplied
1) It isn't as if Christianity was on its last legs. It is, however, shifting from the active religion of Europe and the western hemisphere to the active religion of the global south -- particularly Africa.
2) Christianity is the leading faith, first before Islam, and most people in the world are followers of one religion or another.
3) In some areas, evangelistic Protestantism is supplanting Catholicism (South America). Protestants (Anglicans, Methodists, Lutherans, etc.) who have substantial membership in Africa are being outflanked on their right by conservative churches--not fundamentalist or evangelistic, just more conservative theologically. The consequence is the fracture of groups, like the Methodists, into a new more conservative group and an established mainline group. Sexuality is often the gravel in the gears that leads to rupture,