Shortly before the Brexit referendum, Scotland had an independence referendum, where the Westminster government was in favour of the status quo - and they had a great deal of success by deliberately not figuring out what independence would mean.
What currency would an independent Scotland use? What will happen to their military? What about healthcare, and education? EU membership? What share of the UK's national debt would they take on? Who will get citizenship? What will the border look like? Nobody knows! So a yes vote was a scary leap into the unknown with many unsolved problems, while a no vote was safe and predictable.
After the strategy succeeded in the Scottish independence vote, Cameron decided to repeat that success with Brexit - not figuring out what Brexit means was a deliberate strategy intended to boost the remain campaign.