Disagree completely with the idea that elections are not won on one item in the manifesto - elections are products of time and space and in certain societal conditions they might be won because of broad brush manifesto pledges whereas in others there might be one burning issue and that's the trigger - in the case of the last one it was definitely all about Brexit but very deceitfully crafted to suggest that the winner would be our own wonderful NHS when at the same time the coaches were carrying the banner promising 35M weekly for that institution, talks were already going ahead about continuing the asset stripping that had been in force for the few years previous.
So to those who deny that Brexit was the single issue, look at the record - return to the footage, return to the promise for the NHS and you will see that other things like taxes, education promises, and social care promises (were there any?) had no impact on the way people voted - it was purely the rhetoric about jobs for Brits, power for British courts and money for the NHS - that's it, plain and simple. In a time of relatively political peace, elections are different animals.