David Cameron didn't "win". He lost and then made it someone else's problem.

If it's true that his opposition doesn't want to deal with leaving the EU either, that means they were either too stupid to realize the consequences of what they were promoting (which I find hard to believe), or - if they did realize - they intentionally screwed the UK by having a pissing contest with no idea what to do when they actually won (which I also find hard to believe).