There's no detail behind it, it's so lightweight it's meaningless but it gives your average punter something to get behind, regardless of what it actually stands for. The Tories had obviously been told to repeat it over and over while campaigning. Labour didn't have anything near that.
I'm much more closely aligned to Labour than the Tories but I couldn't articulate what Labour wanted to achieve in a line or two, I doubt Corbyn could. And the majority of people want stuff spoon fed in a soundbite. Get Brexit Done. Very powerful.