Emergence of the Christian Basilica in the Fourth Century

We naturally ask why the Christian basilica emerged. Given its abrupt appearance and immediate standardization, the Christian basilica appears to have been designed for a purpose. If this is so, what we want to know is, [1] for what purpose Christians used basilicas (that is, what happened in Christian basilicas), [2] why they adopted the basilical style for their churches, and [3] why they standardized their design.