Looking at it the wrong way around mate. An awful lot of folk dont bother even reading any manifesto, and after the press when policies are announced, mainly forget all about them. They vote for who they think will represent the UK, and then maybe a big ticket policy. Brexit is obviously the one at the moment.
Johnson knows that. And you can argue till the cows come home about him, but, he appears positive, energised, with pretty much a single message. Corbyn comes across as muddled, railing at the world, and solving problems that the vast majority of folk just dont care about, dont know about, or never affect them.
It isnt right, it isnt a guarantee of even a half decent Government, but unfortunately, tis the world we live in.