"If we can therefore discount the projected economic benefits of either leave or remain then what have people based their decision to leave or remain on?"
The major issue was not wanting to be part of the EU. The vote was for in or out, nuffin about consequences.
Obviously the details are crucial, but as yet each side is not for talking and the clock is running. With or without agreement the clock is running down. The implications have been thrashed out theoretically on here ad nauseam, but it is only opinion.
The vote was not based on economics, it was about regaining control, in or out - yes or no.