Saying that most Brexit voters thought anything about an EEA arrangement is giving them too much credit imo.
Their thought process was as shallow as “we should be independent, get the foreigners out, save EU membership fees, then everything will be good”, with no thought about the reality of the situation and how it will be achieved.
A lot of them wanted hard Brexit just because negotiating a deal was taking too long, because in their minds it’s as simple as just leaving.